Statewide water assessment

              Oklahoma Comprehensive Water Plan
Supplement to Executive Report
Statewide Water Assessment
OCWP Statewide Water Assessment
The following report was developed by the Oklahoma Water Resources Board and CDM, the OCWP’s lead engineering firm, to assess Oklahoma’s water supplies, develop projections of water demands, quantify physical supply shortages, determine the implications of potential climate change scenarios on projected supply and demand, assess anticipated water use permitting and interstate compact restraints, and provide relevant water quality data along with long-term trends.
The Oklahoma Water Resources Board respectfully requests public review of this document. Comments should be provided at any of the thirteen OCWP Feedback and Implementation meetings or in writing to the OWRB by May 31, 2011. Information from this report will be published in the Executive Report of the 2012 Update of the Oklahoma Comprehensive Water Plan.
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Contents
Section 2 – Statewide Water Assessment
2.1 Oklahoma’s Water Supplies .................................................................... 2-1
2.1.1 Surface Water ........................................................................... 2-4
2.1.2 Groundwater ............................................................................. 2-7
2.2 Water Demand Projections ...................................................................... 2-9
2.2.1 Municipal and Industrial ......................................................... 2-10
2.2.2 Self-Supplied Residential ....................................................... 2-11
2.2.3 Self-Supplied Industrial .......................................................... 2-12
2.2.4 Thermoelectric Power ............................................................. 2-12
2.2.5 Agriculture (Livestock and Crop Irrigation) ............................ 2-12
2.2.6 Oil and Gas .............................................................................. 2-12
2.2.7 Summary of Demand .............................................................. 2-13
2.3 Physical Supply Availability Through 2060 ........................................... 2-14
2.3.1 Physical Water Supply Availability Analysis Baseline Scenario ................................................................................... 2-15
2.3.2 Physical Water Supply Availability Results ............................ 2-16
2.3.3 Limitations and Uncertainties in the Physical Water Availability Analyses ................................................................ 2-22
2.4 Climate Change Implications on Supply and Demand ........................ 2-22
2.4.1 Potential Effects on Oklahoma Temperature, Precipitation, and Water Supply .................................................................... 2-23
2.4.2 Potential Effects on Water Demand ...................................... 2-27
2.4.2.1 M&I Demand ........................................................ 2-28
2.4.2.2 Crop Irrigation Demand ....................................... 2-29
2.4.3 Implications for Water Supply Shortages .............................. 2-31
2.5 Permitting and Interstate Compacts ..................................................... 2-31
2.5.1 Water Use Permitting in Oklahoma ........................................ 2-33
2.5.2 Groundwater Permitting Availability ...................................... 2-34
2.5.3 Surface Water Permit Availability ........................................... 2-36
2.5.4 Interstate River Compacts ...................................................... 2-39
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Figures
2-1 Basin-Level Technical Planning Process
2-2 Average Annual Precipitation in Oklahoma
2-3 The 82 OCWP Basins and 13 Watershed Planning Regions
2-4 Oklahoma’s Surface Water Resources
2-5 Average Gaged Stream Flow 1950-2007
2-6 Major Aquifers of Oklahoma
2-7 Oklahoma’s Projected Population and Source of Water Supply
2-8 Statewide Water Demand by Sector
2-9 2060 Basin Demand by Demand Sector and Demand Density
2-10 Maximum Surface Water Gaps, 2060 Baseline Scenario
2-11 Probability of Surface Water Gaps, 2060 Baseline Scenario
2-12 Maximum Alluvial Groundwater Storage Depletions, 2060 Baseline Scenario
2-13 Probability of Alluvial Groundwater Storage Depletions, 2060 Baseline Scenario
2-14 Annual Bedrock Groundwater Storage Depletions, 2060 Baseline Scenario
2-15 Estimated Average Annual Streamflow in 2060
2-16 Estimated Minimum Annual Streamflow in 2060
2-17 Ensemble Climate Change Scenarios
2-18 Potential Change in 2060 Maximum Temperature in August from Historical Average
2-19 Potential Change in 2060 Annual Precipitation from Historical Average
2-20 Potential Change in Surface Water Gaged Flow with Climate Change, 2060 Hot/Dry Scenario
2-21 Potential Change in M&I Demand with Climate Change, 2060 Hot/Dry and Warm/Wet Scenarios
2-22 Potential Change in Crop Irrigation Demand with Climate Change, 2060 Hot/Dry and Warm/Wet Scenarios
2-23 Potential Change in Magnitude of Surface Water Gaps, 2060 Hot/Dry Scenario
2-24 Potential Change in Probability of Surface Water Gaps, 2060 Hot/Dry Scenario (incremental increase in percentage points relative to baseline)
2-25 Groundwater Rights including Aquifer Equal Proportionate Share
2-26 Estimated Available Groundwater in 2060 for New Permits
2-27 Estimated Surface Water Permit Availability Gaps in 2010
2-28 Estimated Available Surface Water in 2060 for New Permits
2-29 Oklahoma's Interstate River Compacts
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Tables
2-1 Major Oklahoma Reservoirs
2-2 Properties of Major Aquifers of Oklahoma
2-3 Statewide M&I Demand Forecast Under Climate Change
2-4 Statewide Crop Irrigation Demand Forecast Under Climate Change
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Section 2
Statewide Water Assessment
The Oklahoma Comprehensive Water Plan (OCWP) assesses and plans for the water needs of all water uses and users in Oklahoma through 2060. Consumptive uses of water are addressed in this section. Nonconsumptive uses are discussed in other sections of the OCWP Executive Report. A reliable water supply is contingent on all of the following aspects:
 Physical water supply availability, or "wet water"
 Permits or water rights to divert water from surface water or groundwater sources
 Infrastructure to divert, treat, and convey the water to its intended use
 Adequate water quality for the intended use
A reliable source of supply must not only have the water physically present for diversion and use, the user must have the permit or water right and the infrastructure to deliver the water, and the water must be of adequate quality. Absent any one of these elements, the supply is not reliable.
Each of these elements was examined at both a statewide and a basin level of analysis as part of the development of the OCWP. The OCWP technical studies used a screening process to evaluate the supply and demand challenges for each basin. Supply options were identified for each basin exhibiting physical water availability shortages, and some basins were identified as having among the most significant challenges in terms of physical availability, permits, and water quality. Supply solutions for these "hot spot" basins, as described in other sections of the OCWP Executive Report, were investigated in further detail. An overview of the technical planning process is shown in Figure 2-1.
2.1 Oklahoma's Water Supplies
Oklahoma's water supplies are driven by the state's diverse climate and influenced by land use, geography, and geology. The state's central location in the United States results in a wide range of precipitation, with areas of the panhandle receiving an annual average of only about 16 inches of precipitation, while the southeastern portion of the state receives an average of over 50 inches (Figure 2-2).
Water supplies can be evaluated using a myriad of different boundaries and geographic extents. For example, one could analyze the sum total of all demand and supplies for the entire state, without further subdivision. However, that level of analysis would not allow an analysis of localized supply and demand issues. In contrast, the analyses could be performed at such a micro-level of analysis (e.g., a single residence) as to not provide practical results. Thus, supply analyses were developed on a watershed or "basin" basis, guided by the location of surface water streamflow gages and availability of acceptable flow data. Similarly, the comparison of supplies and future demand was conducted on a basin basis, requiring the projected water demand to be allocated among those same basins. Section 2
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Figure 2-1 – Basin-Level Technical Planning Process
Figure 2-2 – Average Annual Precipitation in Oklahoma Section 2
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The statewide water supply availability analysis was performed on a geographic basis by subdividing the state into 82 surface water basins using U.S. Geologic Survey (USGS) Hydrologic Unit Code (HUC) 12 boundaries. The basins used for this analysis were adapted from existing Oklahoma Water Resources Board (OWRB) stream system analysis boundaries. Figure 2-3 shows the 82 basins and 13 aggregated Watershed Planning Regions used in the supply availability analyses, including region names and basin numbers.
Figure 2-3 – The 82 OCWP Basins and 13 Watershed Planning Regions
Precipitation strongly influences the state's surface water and groundwater resources. It directly affects surface water supplies via storm runoff and snowmelt. Alluvial groundwater aquifers are made up of sediment deposited by rivers, and are generally filled by surface water or infiltration of precipitation. Bedrock aquifers are typically deeper formations not directly associated with rivers; they are generally filled with water that infiltrates into the aquifer from the surface or other overlying aquifers. Bedrock groundwater typically is somewhat influenced by today's precipitation but more so by broader geologic factors and longer-term climate conditions.
As a key foundation of the OCWP technical work, a database and geographical information system (GIS) based analysis tool was created to compare projected demand to physical supplies for each of the 82 OCWP basins. The "Oklahoma H2O Tool" was used to identify areas of potential shortages (physical water supply availability constraints) and more closely examine demand, supplies, and potential water supply solutions. The supply availability tool was developed to allow flexibility in the performance of a variety of "what-if" Section 2
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scenarios. It provides unprecedented capabilities to make informed decisions based on a variety of factors. The analysis incorporates data on supply and demand to determine the available water (surface water and groundwater) in each OCWP basin.
2.1.1 Surface Water
The extremes of Oklahoma's climate diversity have historically resulted in periods of flooding and extended times of drought. To help address the flow variability inherent in many of Oklahoma's streams and rivers, 34 major storage projects were constructed between 1940 and 1985. Oklahoma has over 3.2 million acre-feet (AF) of water supply storage and over 25 million AF of flood storage (Oklahoma Water Atlas). (An acre-foot is equal to approximately 325,000 gallons.) Oklahoma's major surface water resources and average surface water gaged flows (1950-2007) are shown in Figures 2-4 and 2-5.
Figure 2-4 – Oklahoma's Surface Water Resources Section 2
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Figure 2-5 - Average Gaged Stream Flow 1950-2007
The rivers and streams of eastern Oklahoma typically have higher annual flows than those in western portions of the state. Portions of the Arkansas, Cimarron, and Canadian Rivers systems can generate over 250,000 acre-feet per year (AFY) of runoff. In contrast, in areas of western Oklahoma, significantly less annual flows are typical. For example, during the 2006 drought, some of these river systems experienced a 10-fold decrease or more in total flows.
Information for the state's major surface water storage projects is listed in Table 2-1.
Table 2-1. Major Oklahoma Reservoirs Reservoir Source Purpose Water Supply Storage (1) (AF) Water Supply Yield (AFY) Normal Surface Area (acres) Const. Agency Year Comp.
Arbuckles
Rock Creek
WS, FC, R, FW
62,600
24,000
2,350
USBR
1967
Arcadia
Deep Fork
WS, FC, R
27,380
12,320
1,820
USACE
1984
Birch
Birch Creek
WS, FC, WQ, R, FW
15,165
6,700
1,145
USACE
1977
Broken Bow
Mountain Fork River
WS, FC, P, R, FW
152,500
196,000
14,200
USACE
1970
Canton Lake
North Canadian River
WS, FC, I
97,170
18,480
7,910
USACE
1948
Copan Lake
Little Caney River
WS, FC, R, FW
33,600
21,300
4,850
USACE
1981
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Table 2-1. Major Oklahoma Reservoirs (cont.) Reservoir Source Purpose Water Supply Storage (1) (AF) Water Supply Yield (AFY) Normal Surface Area (acres) Const. Agency Year Comp.
Eufaula
Canadian River
WS, FC, N, P
56,000
56,000
105,500
USACE
1964
Fort Cobb
Cobb Creek
WS, FC, R, FW
78,350
18,000
4,070
USBR
1959
Fort Gibson
Grand (Neosho) River
FC, P
N/A
N/A
19,900
USACE
1953
Fort Supply
Wolf Creek
WS, FC
400
224
1,820
USACE
1942
Foss Reservoir
Washita River
WS, FC, R, I
165,480
18,000
6,800
USBR
1961
Grand
Grand (Neosho) River
FC, P
N/A
N/A
46,500
GRDA
1940
Great Salt Plains
Salt Fork of Arkansas River
FC, WS, FW, R
N/A
N/A
8,690
USACE
1941
Heyburn
Polecat Creek
WS, FC, R, FW
2,340
1,904
880
USACE
1950
Hudson (Markham Ferry)
Grand (Neosho) River
FC, P
N/A
N/A
10,900
GRDA
1964
Hugo
Kiamichi River
WS, FC, WQ, R, FW
121,500
165,800
13,144
USACE
1974
Hulah
Caney River
WS, FC, LF
26,960
18,928
3,570
USACE
1951
Kaw
Arkansas River
WS, FC, WQ, R, FW
203,000
230,720
18,775
USACE
1976
Keystone
Arkansas River
WS, FC, P, N, FW
20,000
22,400
22,420
USACE
1974
Lugert-Altus
North Fork of Red River
WS, FC, I
132,830
47,100
6,260
USBR
1948
McGee Creek
McGee Creek
WS, FC, R, WQ, FW
107,980
71,800
3,810
USBR
1985
Oologah
Verdigris River
WS, FC, N, R, FW
342,600
172,480
31,040
USACE
1974
Optima
North Canadian River
WS, FC, R, FW
76,200
N/A
5,340
USACE
1978
Pine Creek
Little River
WS, FC, WQ, FW, R
70,560
134,400
3,750
USACE
1969
Robert S. Kerr
Main Stem Arkansas River
N, P, R
N/A
N/A
32,800
USACE
1970
Sardis Lake
Jackfork Creek
WS, FC, R, FW
270,270
156,800
13,610
USACE
1981
Skiatook
Hominy Creek
WS, FC, WQ, R, FW
280,200
85,130
10,190
USACE
1982
Tenkiller Ferry
Illinois River
FC, P
25,400
29,792
12,900
USACE
1953
Texoma
Red River
WS, FC, P, N, R, FLOW
150,000
168,000 (2)
86,910
USACE
1944
Thunder-bird
Little River
WS, FC, R
105,900
21,700
6,070
USBR
1965
Tom Steed
Otter Creek
WS, FC, R, FW
88,970
16,000
6,400
USBR
1977
Waurika
Beaver Creek
WS, FC, WQ, R, FW, I
170,200
45,590
10,100
USACE
1977 Section 2
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Table 2-1. Major Oklahoma Reservoirs (cont.) Reservoir Source Purpose Water Supply Storage (1) (AF) Water Supply Yield (AFY) Normal Surface Area (acres) Const. Agency Year Comp.
Webbers Falls
Arkansas River
N, P
N/A
N/A
11,640
USACE
1970
Wister
Poteau River
WS, FC, R, FW
39,082
31,400
7,386
USACE
1949
Total
2,922,637
1,622,968
(1) Includes water quality storage where applicable.
(2) Oklahoma portion of total yield.
N/A - Not Applicable; WS - Water Supply; FC - Flood Control; WQ - Water Quality; R - Recreation; LF- Low Flow Regulation; FW - Fish & Wildlife; P - Power, I - Irrigation, N - Navigation
USBR - U. S. Bureau of Reclamation
USACE - U.S. Army Corps of Engineers
GRDA - Grand River Dam Authority
2.1.2 Groundwater
The major alluvial and terrace aquifers of Oklahoma (Figure 2-6) are in many cases aligned with major surface water features. Both the alluvial groundwater supply and surface water quantities generally increase from west to east across Oklahoma. Major alluvial groundwater aquifers are defined as those with wells capable of yielding 150 gallons of water per minute or more, with the highest yields typically found in alluvial wells along the Arkansas, Canadian, Cimarron, North Canadian, Red River, and Washita Rivers. Alluvial groundwater will continue to be an important supply for all water use sectors.
Figure 2-6 - Major Aquifers of Oklahoma Section 2
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Also shown in Figure 2-6 are the state's major bedrock aquifers, which include the Antlers, Arbuckle-Simpson, Arbuckle-Timbered Hills, Blaine, Elk City, Garber-Wellington, Ogallala, Rush Springs, and Roubidoux. Oklahoma has significant bedrock groundwater resources, with groundwater well yields ranging from less than 50 gallons per minute (gpm) to approximately 1,000 gpm in the Rush Springs aquifer. Bedrock groundwater will be an important future source of supply for Oklahoma; therefore, efficient management of this resource is needed for its continued reliable use.
Table 2-2 lists the state's major aquifers and select aquifer properties. The amount of water that can be recovered from these aquifers varies significantly from one aquifer to another, and can be a function of site-specific hydrogeology and economic feasibility.
Table 2-2. Properties of Major Aquifers of Oklahoma Aquifer Class Type Aquifer Area (acres) Estimated Total Storage (AF)
Antlers
Major
Bedrock
2,723,662
53,589,751
Arbuckle-Simpson
Major
Bedrock
337,629
9,471,084
Arbuckle-Timbered Hills
Major
Bedrock
240,333
961,336
Blaine
Major
Bedrock
465,152
1,402,380
Elk City
Major
Bedrock
193,136
2,243,573
Roubidoux
Major
Bedrock
2,942,358
43,030,750
Rush Springs
Major
Bedrock
1,549,593
79,838,095
Vamoosa-Ada
Major
Bedrock
1,649,642
14,931,579
Garber-Wellington
Major
Bedrock
1,832,124
58,599,398
Arkansas River
Major
Alluvium and Terrace
536,052
945,803
Canadian River
Major
Alluvium and Terrace
1,364,937
5,016,569
Cimarron River
Major
Alluvium and Terrace
832,540
3,858,713
Enid Isolated Terrace
Major
Alluvium and Terrace
51,803
259,793
North Fork of the Red River
Major
Alluvium and Terrace
426,461
3,761,883
Red River
Major
Alluvium and Terrace
884,283
2,591,280
Salt Fork of the Arkansas River
Major
Alluvium and Terrace
541,795
2,191,199
Tillman Terrace
Major
Alluvium and Terrace
182,575
1,283,400
Ogallala
Major
Bedrock
4,376,988
90,590,163
North Canadian River
Major
Alluvium and Terrace
1,254,796
8,286,769
Washita River
Major
Alluvium and Terrace
696,750
4,920,626
Ogallala
Major
Bedrock
4,376,988
90,590,163
Gerty Sand
Major
Alluvium and Terrace
70,416
223,521
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2.2 Water Demand Projections
Key drivers for water planning in Oklahoma include generally increased water demand as a result of population growth and increases in other water use sectors (e.g., agriculture and energy). Figure 2-7 provides a summary of Oklahoma's projected population by supplier source, with the vast majority of Oklahomans being served by a public water supply system. The state's population is expected to grow from 3.7 million in 2009 to 4.8 million in 2060. The five counties with the highest 2009 population were Oklahoma, Tulsa, Cleveland, Canadian, and Rogers (716,704, 601,961, 244,589, 109,668, and 85,654, respectively). The majority of the remaining counties had 2009 populations in the 10,000 – 70,000 range.
Figure 2-7 - Oklahoma's Projected Population and Source of Water Supply
Between 2010 and 2060, the three fastest-growing counties in terms of population are expected to be Oklahoma, Tulsa, and Cleveland (increasing by 122,118, 106,660, and 60,602, respectively). In terms of percent population growth, the three fastest growing counties from 2010 to 2060 are expected to be Love, Marshall, and Texas (232 percent, 123 percent, and 123 percent, respectively). Thirteen of Oklahoma's 77 counties are expected to have less than 10 percent population growth from 2010 to 2060, with one county at zero growth and one county with a slight population decline. Section 2
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Water demand projections for all major water uses throughout the state were developed at 10-year intervals from 2010 to 2060. Water uses are grouped into seven water use sectors. These forecasts were developed for each county in the state, and then allocated to the 82 basins for further planning and analysis. Figure 2-8 summarizes the projected total water demand for the state by water use sector.
Figure 2-8 - Statewide Water Demand by Sector
Overall, by the year 2060, water use in Oklahoma is projected to increase from approximately 1.9 million AFY in 2010 to about 2.5 million AFY by 2060. A brief overview of each demand sector is provided below.
2.2.1 Municipal and Industrial
Municipal and industrial (M&I) demand represents water that is provided by public water systems to homes, businesses, and industries throughout Oklahoma. Water uses include water for bathing, flushing, washing, drinking, landscape irrigation, car washing, recreation, domestic animal care, etc. The quantity of water associated with system losses (e.g., distribution system leakage) and unmetered connections was estimated and included in the M&I demand.
In 2008, as part of the OCWP update, a survey was sent to 785 municipal and rural water providers to collect information on water supply systems across the state. The Oklahoma Rural Water Association (ORWA) and the Oklahoma Municipal League (OML) assisted the OWRB in collecting responses from individual providers. Of the 785 providers receiving a Section 2
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survey, 561 responded. The providers that responded to the survey serve water to about 3,100,000 Oklahomans, or about 86 percent of the state's residents.
The survey was designed to gather information on public water suppliers' planning efforts, supply needs, and infrastructure needs. The OCWP took unprecedented steps to consider the needs of public water suppliers as the OWRB plans for the needs of Oklahoma's citizens now and for the next 50 years. The information obtained from this survey provides foundational data and insights that were used in the following ways:
 Development of county- and provider-level demand projections, using providers' survey responses to estimate existing regional-specific per-capita water demand
 Statewide assessment of public water supply systems, as documented in the report
 Provider-specific information that is documented in the Watershed Planning Region Reports
 Data to make provider-level water use projections, when limited local data are available, for use in their individual planning efforts or project planning in the future
The survey addressed questions related to supplies, demand, infrastructure, and conservation.
Public water supply providers surveyed include municipalities (about 58 percent of respondents), rural water districts (36 percent), and other types of providers (6 percent). Providers that categorized themselves as "Other" include but are not limited to limited service water trusts, government agencies, small water corporations, and non-profit corporations. Overall, the survey captured responses from providers across all regions of Oklahoma.
A majority of providers that presented population projections for future planning horizons expect population increases in the future (87 percent, or 331 of 378 responding providers). However, only a small fraction (6.4 percent) of responding providers have completed a water supply plan in the last 10 years. Increases in water demand are expected, and while many of the responding providers identified excess water treatment plant capacity, 46 percent of responding providers' water distribution infrastructure is greater than 30 years old. In addition to that, half of all reported treatment plants are greater than 30 years old with half of all reported expansions occurring more than 6 years ago. Less than half of the planned distribution system improvements are fully or partially funded (38 percent). Details of the provider survey and its findings are provided in the OCWP Provider Survey Summary Report.
2.2.2 Self-Supplied Residential
This sector includes demand for households on private wells that are not connected to a public water supply system. It is assumed that these households are located primarily in outlying communities and rural areas of the state. While some self-supplied rural Section 2
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residential homes use well water for livestock care, the demand for the self supplied rural residential sector only represent water use inside the home, as well as non-agricultural related outdoor use. Agricultural irrigation and livestock use is described below.
2.2.3 Self-Supplied Industrial
Large industries that are identified as self-supplied users with available water use data and employment counts are included in this group. These industries include sand companies, gypsum production plants, quarry mines, concrete plants, petroleum refineries, paper mills, sawmills, bottling and distribution plants, chemical plants, tire manufacturing plants, lime production, natural gas plants, and meat packing plants.
2.2.4 Thermoelectric Power
Self-supplied and municipal-supplied thermoelectric power producing plants are included in this sector. Water demand estimates are based on megawatt-hours (MWh) produced by each plant and average water needs per MWh, unless substantiated by water use information showing otherwise. Power generation and water use are assumed to have a linear relationship into the future. According to reports from the U.S. Department of Energy, power generation is estimated to grow 1.1 percent annually over the next 30 years. This growth rate is assumed for Oklahoma power generation through 2060.
2.2.5 Agriculture (Livestock and Crop Irrigation)
Agriculture demand is estimated by two sub-sectors: livestock and crop irrigation. U.S. Department of Agriculture (USDA) Census of Agriculture data were utilized for both sub-sectors. Livestock demand is evaluated by livestock group and are based on average day water requirements for each group. Data were obtained from the most recent available Agriculture Census on irrigated acres by crop type by county. These data were combined with crop irrigation water requirements, as published in the Natural Resource Conservation Service (NRCS) Irrigation Guide for Oklahoma. Adjustments were made to the crop requirements to include water losses from on-farm irrigation delivery system inefficiencies.
2.2.6 Oil and Gas
This sector represents water used in oil and gas drilling and exploration activities but does not include water used at oil and gas refineries. Drilling and exploration activities use water for supplemental fluid in enhanced recovery operations, during well drilling and completion, during workover of an oil or gas well, as rig wash water, as coolant for equipment, and for sanitary purposes. Water use from both conventional and unconventional drilling techniques was considered, and projections of drilling activities were provided by representatives of the Oklahoma oil and gas industry.
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2.2.7 Summary of Demand
The county demand for each of the above sectors was also allocated to the OCWP basins for further analysis. A summary of demand projections by basin and demand sector is provided in Figure 2-9. As shown in this figure, Oklahoma's urban areas have relatively high demand densities associated with M&I water use, while western Oklahoma's higher demand density is largely driven by agricultural demand.
Figure 2-9 – 2060 Basin Demand by Demand Sector and Demand Density
Potential uncertainties and limitations associated with the future demand projections for each water use sector for Oklahoma include:
 Potential variation in current M&I per-capita water use estimates between actual usage and usage reported in the Fall 2008 water provider survey, and between current and future rates of use
 Deviation from projected population projections
 Variability in the number of agricultural irrigated acres, depending on economic factors, technology advances, and/or water supply availability
 Potential for future changes in water use efficiencies not reflected in these projections
 Variability in economic conditions, with the potential to affect nearly all water use sectors Section 2
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 Deviation from the assumed future locations and water use for thermoelectric power facilities and other self-supplied industrial water users
Details of the demand forecast methods, sources of data, and results are documented in the OCWP Water Demand Forecast Report.
2.3 Physical Supply Availability Through 2060
As a key foundation of the OCWP technical work, a sophisticated database and GIS based analysis tool was created to compare projected water demand to physical supplies in each of the 82 OCWP basins statewide. Recognizing that water planning is not a static process but rather a dynamic one, this versatile tool can be updated over time as new supply and demand data become available, and can be used to evaluate a variety of "what-if" scenarios at the basin level, such as a change in supply sources, demand, new reservoirs, and various other policy management scenarios.
Called the "Oklahoma H2O Tool," this tool was used in the planning process to identify areas of potential "wet water" shortages (physical supply availability constraints) and a need to more closely examine demand, supplies, and evaluate potential water supply solutions.
Primary inputs to the tool include the demand projections (Section 2.2) for each decade through 2060, founded on widely-accepted methods and peer review of inputs and results by state and federal agency staff, industry representatives, and stakeholder groups for each demand sector. Supply inputs (Section 2.1) include surface water data for each of the 82 basins used 58 years of publicly-available daily streamflow gage data collected by the USGS. As such, these data explicitly include the historical "drought of record" for each of the 82 basins. Groundwater resources were characterized using previously-developed assessments of groundwater aquifer storage and recharge rates.
Current demand, diversions, return flows, and alluvial groundwater/surface water physical interactions are physically manifested in the streamflow record. The tool takes those monthly streamflow data and subtracts out the projected monthly surface water and alluvial groundwater demand to estimate the stream flow that will be available in that future planning year. The analysis also compares monthly bedrock groundwater demand to monthly bedrock aquifer recharge rates.
The analysis was conducted using historical hydrology data from water year 1950 through water year 2007, and applying future changes in demand for planning horizons between 2010 and 2060. As opposed to a "calendar year," a "water year" begins in October and ends in September. For example, water year 2006 began in October 2005 and ended in September 2006. The analysis was conducted on a monthly time step, recognizing that both demand and supplies can vary dramatically from one part of the year to another. Section 2
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The water supply availability analysis represents a statewide screening-level of analysis. By its nature, such a statewide analysis has several simplifying elements. Examples of some of the primary considerations in this statewide screening analysis include:
 Water rights or permit obligations are not constraining for purposes of the physical supply availability assessment, but are described in Section 2.5.
 Non-consumptive uses such as instream flows are considered outside the physical supply availability assessment, documented in other sections of the OCWP Executive Report.
 Changes in groundwater aquifer volumes and water levels are not explicitly tracked (i.e., the tool does not calculate the water level of an aquifer at any future date).
Multiple quality assurance (QA) processes were used in developing the Oklahoma H2O Tool, including detailed review by technical experts not involved in the development of the Tool. QA was performed on the Tool’s capabilities, methodology, logic, and assumptions at several points during its development. In addition, the programming of the database tool was conducted using industry best practices for software development, including standard organization, internal code documentation, and display settings for the graphical user interface. Similar extensive tool QA measures were conducted on the input data to the Oklahoma H2O Tool. Input data QA procedures included internal and external review of the demand projections, surface water and groundwater supply estimates, basin formulation, and all other aspects of the input data. Multiple quality control (QC) processes were used to validate the programming of the Oklahoma H2O Tool. QC validation was performed with each update to the Tool.
The primary objectives of the physical supply availability analysis are to characterize statewide physical water supply availability through the 2060 planning horizon, compare these supply projections with demand projections, and quantify anticipated gaps in physical supply. The following sections describe the basis of those analyses, the results of those analyses, and known limitations of the methods and results. Additional information regarding the projected timing, magnitude, and probability of projected shortages in each basin is provided in the Watershed Planning Region Reports.
2.3.1 Physical Water Supply Availability Analysis Baseline Scenario
The Oklahoma H2O physical water supply availability tool provides the ability to analyze any of a number of scenarios and potential future conditions. The following conditions were used to assess physical supply availability under the baseline scenario:
 The current proportion of sources (percent surface water vs. alluvial groundwater vs. bedrock groundwater) for supplying existing demand (by basin and demand sector) will be used to meet future demand. Section 2
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 In-basin local supplies and existing inter-basin transfers were used to satisfy the receiving basin's incremental demand (2007 to 2060) up to the permitted inter-basin transfer capacity.
 Return flows from a given basin's demand (e.g., M&I treated wastewater discharges) are delivered to the next downstream basin.
 The change in upstream demand affects the supply availability downstream. For example, return flows generated in a basin will continue to flow downstream until the supply is used.
 Supplies in bedrock groundwater aquifers are not hydrologically connected to surface water.
 Future demand are supplied by water from the basin that generates the demand (i.e., we are characterizing the gap that would be expected to occur if all new demand were satisfied with local sources and existing inter-basin transfers).
 All effects of well pumping remain in the basin where a well is located.
A surface water gap occurs in any month where demand on surface water supplies exceeds the physically available surface water supply in the basin. The maximum annual surface water gap for the period of record is defined as the maximum of the sum of the monthly gaps for a given year. Alluvial groundwater and bedrock groundwater shortages are referred to as depletions, rather than gaps. An alluvial groundwater or bedrock groundwater depletion occurs when the demand exceeds the aquifer recharge rate, at which point the demand draws supplies from aquifer storage and reduces the amount of water in storage. Over time, continued depletions will draw down stored supplies in the aquifer and may result in continued use of the wells being physically or economically infeasible.
None of the analyses presented in this section is intended to indicate the permit or economic availability of water under Oklahoma's existing water administrative system. Rather, these analyses focus on the physical availability of surface and groundwater supplies. Analyses of permit availability are documented in Section 2.5.
2.3.2 Physical Water Supply Availability Results
Evaluations of the baseline physical supply availability through the OCWP 50-year planning period document the potential for shortages in the ability of surface water and groundwater supplies to meet Oklahomans' growing water demand. Specifically, the baseline analyses portray the potential shortages if local sources and existing inter-basin transfers are used to meet future demand, with local groundwater and surface water resources used in their same proportions (albeit increasing quantities) currently used to satisfy each demand sector's water needs in the basin. Section 2
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Alluvial groundwater aquifers have a hydrologic connection with the overlying streams and rivers. Thus, the physical water supply availability analyses recognize that alluvial groundwater depletions can deplete surface water flows. The interaction of alluvial groundwater depletions and surface water flows is complex and changes over time depending on the location and rate of alluvial groundwater depletions and on the surface water flows themselves. Even so, alluvial groundwater demand from well pumping eventually is supplied by the flow in streams or from recharged water that would have discharged to streams. This analysis incorporates the alluvial groundwater-surface water connection by attributing all alluvial groundwater demand to streamflow.
Bedrock groundwater aquifers in Oklahoma, for the most part, do not have a direct hydrologic connection to overlying surface water. Bedrock groundwater aquifers are replenished slowly by recharge from surface infiltration and from adjacent aquifers. This analysis evaluates bedrock groundwater depletions using projected bedrock groundwater demand in comparison to the estimates of annual recharge to bedrock groundwater aquifers. Depletions to bedrock groundwater aquifers are tabulated in comparison to estimates of the volume of water in storage in these aquifers.
Both the magnitude and the probability of supply shortages and depletions are important considerations in water supply planning. For instance, many communities or water users would invest in infrastructure or additional conservation programs to mitigate shortages if they were anticipated to be high in both magnitude and probability. However, investments in infrastructure to mitigate a low-probability, high-magnitude shortage may not be economically feasible, depending on local conditions and priorities. Rather, such shortages might be addressed by temporary demand management measures such as outdoor watering restrictions during drought. Potential solutions for addressing anticipated supply needs are addressed on a basin level in the Watershed Planning Region Reports.
Shortages for the baseline scenario under 2060 demand conditions are summarized graphically for the state in Figures 2-10 through 2-14. Additional detail on the magnitude and probability of surface water gaps and groundwater depletions by basin and decade is provided in the Watershed Planning Region Reports.
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Figure 2-10 - Maximum Surface Water Gaps, 2060 Baseline Scenario
Figure 2-11 - Probability of Surface Water Gaps, 2060 Baseline Scenario Section 2
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Figure 2-12 - Maximum Alluvial Groundwater Storage Depletions, 2060 Baseline Scenario
Figure 2-13 - Probability of Alluvial Groundwater Storage Depletions, 2060 Baseline Scenario Section 2
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Figure 2-14: Annual Bedrock Groundwater Storage Depletions, 2060 Baseline Scenario
An estimate of the surface water flow at each of the 82 OCWP surface water gages in 2060 is presented in terms of the annual average flow and the minimum annual flow in Figures 2-15 and 2-16, respectively. These projections are based on flow data for the 58-year period of record at each OCWP stream gage location and the projected surface water use in each basin in 2060. The minimum streamflow shown for each basin is an estimate of the minimum flow for that basin under any of the 58 years of historical hydrologic data, and as such, the minimum flows shown in the figure would likely not occur for all 82 basins in any single future calendar year. Surface water gaps are calculated based on a monthly comparison of surface water demand to gaged flow. Therefore, gaps may occur in any basin, including those for which minimum annual flows are projected to be greater than zero. Section 2
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Figure 2-15– Estimated Average Annual Streamflow in 2060
Figure 2-16 – Estimated Minimum Annual Streamflow in 2060 Section 2
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2.3.3 Limitations and Uncertainties in the Physical Water Availability Analyses
There are several known limitations and uncertainties associated with the physical water supply availability methodology and input data. The key limitations include:
 Localized surface water shortages or groundwater depletions may not be evident at the basin level, such that the magnitude and/or probability of localized shortages might be greater than those shown via this analysis for each OCWP basin.
 Future proportions of surface water and groundwater used to satisfy future demand for a given basin and water use sector may differ from current proportions.
 The Red River is not considered a water supply source, due to high salinity and other issues.
 GRDA contracts are implicitly included in the input dataset using surface water diversion amounts identified in the OWRB Water Rights database.
 Drawing down the water in a reservoir may influence the timing or quantity of gaps, especially when the majority of consumptive use occurs upstream of the stream gage.
 Upstream states were assumed to use 60 percent of all available flow into Oklahoma based on OWRB's permitting protocol, which is adapted from interstate compact obligations between Oklahoma and its neighboring states.
 Downstream interstate compact obligations were assumed to not constrain availability and were analyzed separately as part of the permit availability analyses.
2.4 Climate Change Implications on Supply and Demand
In recent years, significant national and international scientific efforts have been undertaken to understand and characterize the potential implications of climate change on water resources. A wide range of models and assumptions are being used by the scientific community to estimate future temperatures, precipitation quantities and patterns, and other factors affecting water supply and demand. The Oklahoma Climatological Survey (OCS; http://climate.ok.gov) has conducted a review of the current assessments of climate change research and concludes the following to be true:
 The earth's climate has warmed during the last 100 years;
 The earth's climate will very likely continue to warm for the foreseeable future;
 Much of the global average temperature increases over the last 50 years can be attributed to human activities, particularly increasing greenhouse gases in the atmosphere; and
 Oklahoma will be impacted. Section 2
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In particular, climate change is projected to continue to alter the water cycle across the U.S., including the total amount of annual precipitation, timing of the precipitation, precipitation intensity and probability, and location of precipitation. Nationwide, most locations already have experienced increases in both precipitation and streamflow and decreases in drought during the second half of the 20th Century.
The U.S. Global Climate Research Program (USGCRP) projects that more frequent heavy rainfall events and droughts will affect much of the Great Plains as climate changes. The USGCRP notes, "Projections of increasing temperatures, faster evaporation rates, and more sustained droughts brought on by climate change will only add more stress to overtaxed water sources."
A variable precipitation history and an uncertain future under climate change combine to challenge even the most forward-thinking and resourceful managers of resources and infrastructure. While there remains significant uncertainty in the potential range of climate change impacts, particularly with regard to changes in precipitation, a sensitivity analysis of the possible effects of climate change was undertaken as part of the OCWP technical studies. By assessing sensitivity of potential impacts on both water supply and water demand from projected changes in climate, the OCWP is providing some insights into the degree to which the balance of water supply and water use might change should those projections hold true.
2.4.1 Potential Effects on Oklahoma Temperature, Precipitation, and Water Supply
According to a recent report by USBR, review of current downscaled climate projections over Oklahoma suggests that the southern Great Plains are likely to be warmer in the future, although the rate of warming varies. Projections of precipitation differ from model to model and range between drier and wetter than historical conditions (USBR Technical Memorandum 86-68210-2010-01).
In order to assess the potential implication of surface water availability under climate change conditions, five climate change scenarios were developed based on ensembles of climate projection models. The scenarios were developed from a set of readily-available downscaled projections obtained from the bias-corrected and spatially downscaled WCRP CMIP3 Climate Projections archive (WCRP CMIP3, 2009) described by Maurer et al (2007). At the time of this study, the archive contained 112 projections of monthly temperature and precipitation, with each projection consisting of an overlap period of 1950 through 1999 and a projection period of 2000 through 2099.
The WCRP archive contains statistically downscaled and bias-corrected data developed jointly by USBR, Santa Clara College, and the Lawrence Livermore National Laboratory. WCRP-CMIP3 archive has been developed using peer reviewed methods (Maurer et al., 2002) and is currently being used by USBR and many other entities for climate change impact analyses. Section 2
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The five scenarios were developed for two different projection horizons: 2030 and 2060. Four of the scenarios link to representative ensembles of projections along a range of potential temperature and precipitation conditions. Q1 is a hot and dry scenario; Q4 is a warm wet scenario; and Q2 and Q3 are intermediate scenarios. The fifth scenario, "C," is the central tendency of Q1-Q4.
The OCWP methodology for developing climate projections closely followed that applied by USBR as part of their "ensemble hybrid-delta" method (USBR Technical Memorandum 86-68210-2010-01). Projections were developed based on differences in regional mean annual temperature and precipitation compared to the historical baseline (Figure 2-17). Q1 represents the ensemble projection developed from the set of individual projections with predicted mean annual temperature changes greater than the median projected change (upper half) and predicted mean annual precipitation changes less than the median projected change (lower half) (i.e., hot and dry). Similarly, Q2 is developed from the lower half of both the temperature and precipitation change; Q3 from the upper half of both temperature and precipitation change (hot and wet); and Q4 from the lower half of temperature change and upper half of precipitation change (warm and wet). The C scenario represents the pool of projections from the interquartile range of change projections: 25th to 75th percentile of both temperature and precipitation change.
Figure 2-17 - Ensemble Climate Change Scenarios
For each of the five scenarios, and each month, climate adjustment factor distributions were calculated based on differences between the ensemble pools of data and the historical baseline data set. These adjustment factors were then applied to the historical timeseries data set to incorporate climate change impacts associated with the given planning horizon, while maintaining historical patterns of month-to-month variability. To bracket the range of potential climate projections and in light of the uncertainties in Section 2
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climate change projections, the Q1 (Hot/Dry) and Q4 (Warm/Wet) scenarios were selected for estimating potential future conditions in Oklahoma.
The impact on temperature and precipitation under the Q1 and Q4 scenarios was used to estimate the potential implications on both surface water supply and water demand across Oklahoma. The potential change in 2060 maximum temperature in August from the historical average is depicted in Figure 2-18 for the Q1 and Q4 scenarios. Similarly, Figure 2-19 shows the potential change in annual precipitation from the historical average for these scenarios.
Figure 2-18 - Potential Change in 2060 Maximum Temperature in August from Historical Average
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Figure 2-19 - Potential Change in 2060 Annual Precipitation from Historical Average
A hydrology model was used to quantify the sensitivity of runoff to changed climate conditions. This sensitivity was expressed as a set of changes in runoff that were estimated by comparing simulated runoff based on the historical weather record with simulated runoff based on an adjusted weather record that reflects projected changes in climate. This approach compensates for some of the unavoidable bias inherent in any hydrology model.
This work employed a physical process-based hydrology model, the Variable Infiltration Capacity (VIC) macro-scale hydrology model. The VIC model is a distributed (gridded) macro-scale (regional-scale) physical hydrology model with several applications to climate change studies and successful application to numerous basins around the world.
The VIC model operates on each grid cell independently. The scale of the grid cells may be varied depending on the application, but in this work, the model was constructed on a 1/8°spatial resolution, which is roughly a square 8 miles (12 kilometers) on a side. In this work, the VIC model was run on a daily time step. Runoff was aggregated by stream basin and to a monthly time step.
The estimated sensitivity of runoff to projected climate change was quantified by making two runs of the hydrology model, one that used the historical weather record (the baseline Section 2
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case) and a second that used a projected weather record (the projected case; as is described below, these two records are the same length and each month in the projected record corresponds to the same month in the historical record). For each month in the historical record the sensitivity of runoff to climate change is expressed as the ratio between the runoff simulated using the projected record and the runoff simulated using the historical record.
The projected effects in 2060 on surface water flows, expressed as a change relative to the 1950-2007 historical average, are depicted in Figure 2-20 for the Hot/Dry (Q1) scenario, indicating a possible upper end of impacts to Oklahoma's surface water supplies. Additional information and projections for other scenarios and the 2030 timeframe are provided along with detailed explanations of the methods and results of the climate change impacts in the OCWP Climate Impacts to Streamflow Report.
Figure 2-20 - Potential Change in Surface Water Gaged Flow with Climate Change, 2060 Hot/Dry Scenario
2.4.2 Potential Effects on Water Demand
Recognizing that changes in our climate would affect both Oklahoma's water supplies and demand, OCWP technical analyses also considered the potential for climate change to affect certain demand sectors' forecasted water use. Specifically, the M&I and Crop Irrigation demand sectors were analyzed for how they could change under the Hot/Dry (Q1) and Warm/Wet (Q4) climate change scenarios. These two demand sectors were analyzed because they both include outdoor irrigation that has the potential to be significantly affected by climate change. The state's other five demand sectors may be affected to some degree by climate change, but those impacts would be expected to be Section 2
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much less significant than the M&I and Crop Irrigation demand sectors. Moreover, these two demand sectors together comprise over two-thirds of Oklahoma's water demand, such that the demand sectors that would be most significantly affected by climate change are also the major drivers of water use in Oklahoma.
2.4.2.1 M&I Demand
Statistical results of the OCWP Climate Demand Model were used to model the impacts of climate change on M&I water demand. The Climate Demand Model was developed using regression analysis and assessed the relationship between weather and monthly water demand for five communities in geographically diverse areas of Oklahoma. Details of the Climate Demand Model are documented in the OCWP Weather Production Model Revised Final Technical Memorandum. The relationships between M&I demand and historical weather are expressed as elasticities, or the percent change in monthly water demand given a unit change in monthly weather.
Variation in both monthly average daily maximum temperature and monthly total precipitation were found to have statistically significant relationships with water production. The elasticities for maximum temperature and precipitation were used to adjust monthly water demand estimates for the potential shifts in maximum temperature and precipitation.
Table 2-3 provides the statewide M&I demand forecast summary for the Hot/Dry (Q1) and Warm/Wet (Q4) climate scenarios as well as the difference from the baseline forecast. As expected, the 2060 Hot/Dry scenario produces the largest increase in M&I demand. The projected 73,256 AFY increase in 2060 demand under the Hot/Dry scenario is significant, equivalent to the projected increase in demand under the baseline (no climate change) scenario of about 20 years of M&I demand growth across Oklahoma. The change in M&I demand from baseline under climate change scenarios statewide are displayed in Figure 2-21. The county-level demand projections were subsequently allocated to the 82 OCWP basins for an evaluation of potential shortages under climate change conditions.
Table 2-3. Statewide M&I Demand Forecast Under Climate Change Year Baseline (AFY or %) Hot/Dry (AFY or %) Warm/Wet (AFY or %)
2030
682,391
718,747
699,119
2060
772,773
846,029
805,398 Change from Baseline
2030
N/A
36,356
16,727
2060
N/A
73,256
32,625 Percent Increase from Baseline
2030
N/A
5.3%
2.5%
2060
N/A
9.5%
4.2%
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Figure 2-21 - Potential Change in M&I Demand with Climate Change, 2060 Hot/Dry and Warm/Wet Scenarios
2.4.2.2 Crop Irrigation Demand
Modeling climate change impacts on agriculture demand required adaptation and use of the model developed for the OCWP baseline forecast. Climate change is assumed to impact only the Crop Irrigation demand and no change is assessed for the Livestock demand sector. The model considers a county's number of acres to be irrigated in the future, relative crop mix, monthly irrigation requirements for each crop, and losses due to irrigation system inefficiencies. The baseline forecast used monthly irrigation requirements for crops at 11 stations throughout Oklahoma, as reported in the NRCS Irrigation Guide Report, Oklahoma Supplement (Natural Resource Conservation Service, 2006).
For the climate change scenario forecast, it was assumed that the number of irrigated acres, relative mix of crops, and irrigation efficiencies would remain constant from the baseline forecast. Irrigation crop requirements by station were assumed to change given climate change scenarios. Changes to the baseline demand forecast for Crop Irrigation demand across all of Oklahoma's counties were calculated using NRCS methods and the climate inputs described in Section 2.4.1. Those changes were then applied to the baseline demand to determine the projected demand for Crop Irrigation under climate change conditions.
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Table 2-4 provides a statewide summary of Crop Irrigation demand under baseline, Hot/Dry, and Warm/Wet conditions. The projected 143,567 AFY increase in 2060 demand under the Hot/Dry scenario is significant, equivalent to the projected increase in demand under the baseline (no climate change) scenario of about 50 years of Crop Irrigation demand growth across Oklahoma. The change in Crop Irrigation demand from baseline under climate change scenarios statewide are displayed in Figure 2-22. The county-level demand projections were subsequently allocated to the 82 OCWP basins, using the same methods employed for allocating baseline county demand values to baseline basin-level demand forecasts.
Table 2-4. Statewide Crop Irrigation Demand Forecast Under Climate Change Year Baseline (AFY or %) Hot/Dry (AFY or %) Warm/Wet (AFY or %)
2030
806,112
892,221
823,622
2060
897,464
1,041,032
926,557 Change from Baseline
2030
N/A
86,109
17,511
2060
N/A
143,567
29,093 Percent Increase from Baseline
2030
N/A
10.7%
2.2%
2060
N/A
16.0%
3.2%
Figure 2-22 - Potential Change in Crop Irrigation Demand with Climate Change, 2060 Hot/Dry and Warm/Wet Scenarios Section 2
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2.4.3 Implications for Water Supply Shortages
Ultimately, the effects of climate change on Oklahoma's surface water supplies and water demand could affect the shortages users will face in the future. To characterize those possible implications, projections of monthly surface water flow for each of the 82 OCWP basins under climate change were input into the Oklahoma H2O tool, along with projections of demand under climate change conditions. Other than the climate change-driven adjustments to surface water supply (streamflow data), Crop Irrigation demand, and M&I demand, no other modifications were made relative to the baseline scenario for projecting future water shortages under climate change. Specifically, the changes in the surface water gaps in each basin were examined for 2030 and 2060 conditions under the Hot/Dry and Warm/Wet scenarios.
Impacts on surface water gaps are expected to be most significant under the Hot/Dry scenario, and are anticipated to increase in their severity over time. Figures 2-23 and 2-24 depict the potential change in surface water gaps under Hot/Dry climate change supply and demand conditions, relative to the baseline scenario. Figure 2-23 shows the change in the magnitude of surface water gaps under the 2060 Hot/Dry scenario. Figure 2-24 depicts the change in probability of surface water gaps under the same conditions, where the increase is expressed as an incremental increase in percentage points. For example, if a basin's probability of gaps increased from 40 percent (baseline) to 50 percent (climate change), the figure would indicate an increase of 10 percentage points. In light of the potential impacts on supplies and demand, Oklahoma water planners at the federal, state, and local level should continue to monitor climate change science and adapt their planning as more data become available.
2.5 Permitting and Interstate Compacts
The state's overall supply availability is also influenced by Oklahoma's water laws and federally enforced Interstate Compacts. This section summarizes the results of analyses of the permit availability of water supplies in Oklahoma relative to water rights, and the implications of the state's Interstate Compacts. A water right can be a permit, prior right (groundwater), or vested right (surface water). The permit availability was evaluated in parallel with the physical water supply, water quality, and infrastructure constraints. Interstate Compacts describe how we share water between our neighboring states and identify what is available for use in Oklahoma. Oklahoma is party to four Interstate Compacts. Physical water availability and water quality constraints are discussed in Sections 2.3 and 2.6, respectively.
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Figure 2-23 - Potential Change in Magnitude of Surface Water Gaps, 2060 Hot/Dry Scenario
Figure 2-24 - Potential Change in Probability of Surface Water Gaps, 2060 Hot/Dry Scenario (incremental increase in percentage points relative to baseline)
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The permit availability analyses consisted of the following aspects:
 Identification of the maximum amounts of surface water and groundwater that could be permitted using Oklahoma's existing statutory requirements and water rights permitting protocol
 Documentation of interstate river compact agreements and obligations
The maximum amount of surface water and groundwater available for permitting may change if statutory or rule changes occur in the future. Tribal issues were investigated separately and are documented in other sections of the OCWP Executive Report. The results of the tribal investigations could affect this analysis and should be considered upon their completion, and/or as part of OCWP implementation activities. Additionally, the riparian rights doctrine, which is not evaluated in this report, could affect the findings of these analyses. Results could also vary as additional aquifers are studied and temporary permits are converted to regular permits.
The maximum amount of water that could be permitted was compared to demand forecasts for 2060, for each of the 82 OCWP basins, to check for constraints of the current permitting system on meeting future demand. Interstate river compacts were also summarized as part of this effort, and Oklahoma's anticipated surface water development was compared to interstate river compact obligations to check whether interstate river compact requirements are likely to constrain the use of supplies to meet anticipated demand for surface water in Oklahoma.
Details of the permit availability and compact analyses are documented in the OCWP Water Supply Permit Availability Report.
2.5.1 Water Use Permitting in Oklahoma
Oklahoma water law considers surface water and groundwater separately. Stream water, the term used in surface water permits, is "water in a definite stream and includes but is not limited to water in ponds, lakes, reservoirs, and playa lakes" (Oklahoma Administrative Code 785:20-1-2.Definitions). Surface water is a public resource that is subject to appropriation by the OWRB. Oklahoma surface water laws are based on riparian and prior appropriation doctrines. OWRB issues a permit, also referred to as a water right, to divert water from a stream for beneficial use. Domestic use of groundwater or surface water by individuals for household purposes, lawns, orchards, and cattle watering up to the normal grazing capacity, plus use of up to 5 AFY for agriculture by natural individuals, firefighting, and use by non-individuals for drinking water, restrooms, and lawn watering does not require a permit. New surface water permits may not interfere with existing permitted withdrawals, domestic users, and reservoir yields. If the beneficial use of the diversion is not maintained, the law specifies that permitted withdrawal amounts are forfeited.
Groundwater is considered a property right in Oklahoma. Groundwater is defined as "fresh water [less than 5,000 parts per million total dissolved solids (TDS)] under the surface of Section 2
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the earth regardless of the geologic structure in which it is standing or moving outside the cut bank of any definite stream." The amount of groundwater that may be withdrawn is based on the number of acres of land overlying the groundwater basin. OWRB permits the withdrawal of groundwater providing that the following are satisfied:
 The party requesting the permit owns or leases the land (or has right to the water under the land)
 The land lies atop a groundwater basin or sub-basin
 The use will be beneficial
 No unauthorized use of wells or groundwater (waste by depletion)
 No pollution to the basin or aquifer (waste by pollution) (82 O.S., §1020.9)
In addition to the merits of the groundwater permit, the potential for interference with existing wells may be examined. Well pumping can be curtailed to less than the permitted amount if interference with existing wells occurs. New wells in aquifers where an equal proportionate share (EPS) has been established are required to be located at least a 1/4 mile away from the next nearest existing well to avoid such interference, unless otherwise proven in a hearing before the OWRB.
Two major types of groundwater permits are issued by the OWRB—regular and temporary. Regular groundwater permits are issued for aquifers that have been studied and an EPS defined. An EPS is the portion of maximum annual yield of groundwater in a given groundwater basin allocated to each acre of overlying land. The groundwater basins with an EPS, which currently vary from 0.5 to 2.1 AFY per acre, are shown in Figure 2-25. In all areas with no defined EPS, a temporary permit of 2.0 AFY per acre may be issued. If the land overlies more than one aquifer, separate permits are issued for each aquifer that is used in studied basins. Pumping of groundwater for domestic uses is exempt from the OWRB groundwater permitting process, but domestic users are not allowed to waste groundwater.
2.5.2 Groundwater Permitting Availability
The permit availability of groundwater was determined for each of the 82 OCWP basins, including areas with and without studied groundwater basins. The OCWP basins were defined based on surface watersheds. Therefore, Oklahoma's groundwater aquifers typically span multiple OCWP basins.
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Figure 2-25 –Groundwater Rights including Aquifer Equal Proportionate Share
To calculate the maximum permit groundwater availability (quantity that could be permitted), a hypothetical regular or temporary permit was assigned to the entire state. Areas with regular permits were determined from the OWRB major and minor aquifer GIS data files. EPS groundwater withdrawals were calculated by multiplying the area of the groundwater basin in each OCWP basin by the EPS. Temporary permit withdrawals were calculated by multiplying the remaining area of each basin by 2 AFY per acre. The total permit availability was determined by summing the temporary and EPS withdrawal volumes. The total permit availability therefore effectively includes amounts that could be authorized by the two major types of permits. The current permit availability (2007) was estimated by subtracting the existing active groundwater rights from the total permit availability. Since forfeiture of existing groundwater rights is rare, all existing active rights were used to conservatively represent the current portion of each basin that is not available for permits.
The quantity of groundwater that would need to be permitted by 2060 was estimated for each OCWP basin by summing the existing active groundwater rights and the increase in projected groundwater demand from 2007 to 2060. Demand increases were calculated using the current (2007) surface water and groundwater supply proportions in each OCWP basin.
A groundwater permit gap was estimated for the present (2010) and long-term (2060). The permit availability gap was calculated by subtracting the projected 2060 estimated groundwater permits from the total quantity that could be permitted in each OCWP basin. Since some existing rights are not 100 percent utilized, the projected 2060 groundwater Section 2
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permits used in this analysis may be greater than the projected future groundwater demand and thus provides a conservative forecast.
The groundwater permit availability analyses identified no groundwater permitting gaps in the state in the near-term or long-term timeframe. Projected groundwater demand in 2060, assuming the continued use of the current supply proportions of surface water and groundwater sources in each basin, could be fully permitted using current law and permitting protocol. The estimated amount of groundwater that will be available for new permits in 2060 in each basin is shown graphically in Figure 2-26. As the remaining aquifers are studied and assigned an EPS, the available water for permits may increase or decrease relative to the temporary permit value of 2.0 AFY per acre.
Figure 2-26 – Estimated Available Groundwater in 2060 for New Permits
2.5.3 Surface Water Permit Availability
The surface water permit availability was determined for each of the 82 OCWP basins. Future surface water withdrawals may not impact existing surface water rights as they would be junior to existing water rights. Therefore, the obligations both upstream and downstream were considered. Those obligations include existing active permits, potential future permits defined by the demand projections, domestic water use, interstate river compact obligations, and reservoir dependable yields.
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The quantity of surface water that would need to be permitted by 2060 was estimated for each OCWP basin using the following methodologies that follow OWRB surface water permitting protocol:
 Existing active rights were allocated to each basin by the location of the SW withdrawal, which was available from the OWRB water rights database.
 The estimated SW permits that will be needed in 2060 was determined by summing the existing active SW rights (annual quantity) and the increase in total SW permit need from 2007 to 2060, which was calculated based on existing schedules of use and SW demand projections. Since some existing rights are not currently 100 percent utilized, the estimated 2060 SW permit need that was estimated for this analysis may be greater than the projected total future demands and thus provides a conservative forecast.
 Existing active SW rights were used to represent the current SW that is unavailable for new permits. The unavailable water includes the amount of permitted water listed in schedules of use for the given analysis year. OWRB undertakes systematic reviews of permits to assure beneficial use of the water, and portions of permits that are not used for beneficial use or covered in a schedule of use may be forfeited.
 The increase in total SW permit need was calculated in two parts: projected increases in non-municipal and industrial (M&I) demands, such as Crop Irrigation, and projected increases in M&I demands or existing schedules of use. Future SW permits from non-M&I demands were calculated as the increase in non-M&I demand from 2007 to 2060 using the current (2007) SW and GW supply proportions. Future SW permits from M&I demands were calculated as the larger of (1) the increase in active permitted diversions due to schedules of use from 2007 to 2060, or (2) the increase in M&I demand from 2007 to 2060 using the current (2007) SW and GW supply proportions for each basin.
 Oil and Gas users currently use 90-day temporary permits for well drilling and development activities. Oil and gas activities were assigned a general permit for consistency in the analysis, where the general permit amount is equal to the sum of the 90-day permits for the year.
 Upstream and downstream rights were included as permit obligations for each basin. OWRB applies case-by-case analyses when permitting on the mainstem of a river, which includes the OCWP basin's outlet. To systematically account for mainstem permitting on a statewide basis, all upstream basins were taken into account. The immediate downstream basin was included in the basin's permit obligation. Permit availability gaps due to downstream basin's estimated future permits were flagged as a mainstem restriction.
 Domestic uses were calculated as 6 AFY per quarter section (160 acres) of the total basin area. Non-consumptive uses were not incorporated in the analysis, consistent with current law and permitting practice. Section 2
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 Consistent with OWRB methodology and assumptions to recognize typical compact apportionment provisions, upstream states are typically recognized to be able to use 60 percent of the measured historical stream flow at the Oklahoma border; however, actual compact provisions are reviewed on an ad hoc basis for potential availability issues. The presumed reduction in flow is then accounted for in all downstream basins within Oklahoma.
 Arkansas was allocated (for purposes of this report) 40 percent of runoff generated in OCWP basins 44, 45, 46, 47, and 82 based on the Arkansas River Basin Compact between Arkansas and Oklahoma. Runoff is defined for purposes of this report only as the measured stream flow. This is a conservative assumption because return flows from uses in the basin will result in higher measured flows.
 Downstream states on the Red River were allocated (for purposes of this report only) 40 percent of runoff generated in basins 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and 13. Runoff was defined as the measured stream flow. Note, the above methodology is a simplification of the compact apportionment provisions. The Red River Compact has a different definition of runoff, and "undesignated flow" is separately defined in the Red River Compact for the apportionment provisions.
 Reservoir dependable yields from the OWRB water rights database were used. The yields reflect all reservoir conservation pool allocations (irrigation, water quality, water storage, etc.). Reservoir dependable yields and associated permits were not double counted.
 NRCS reservoirs without dependable yields were included based on their normal storage volume. NRCS reservoirs and associated permits were not double counted. Permits were associated with NRCS reservoirs based on being within a half mile of the reservoir dam location.
 Upstream estimated future permits were accounted for in all downstream basins.
 Permit availability was not analyzed for GRDA’s area of responsibility (Basins 80 and 81).
For each basin, the estimated 2060 SW permit need was subtracted from average annual measured historical streamflow (adjusted based on the presumed compact constraints) to determine the SW permit availability gap. Average annual stream flow (using data from 1951 through 1980 per OWRB protocol at the time of this analysis) was determined from the monthly SW supplies calculated separately in the physical supply availability analysis. Average annual stream flows were used in this analysis, following OWRB permitting protocol.
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The estimated gaps in SW permits in 2010 are presented in Figure 2-27. The estimated available streamflow for new permits in 2060 is presented in Figure 2-28. This represents the SW that could be permitted in a given basin after satisfying existing permits and schedules of use, and after satisfying the amount of new permits that would be needed to accommodate the basin’s projected growth in SW use from 2010 through 2060. New permits to accommodate the projected growth in SW use were assumed to be needed only to the degree that existing rights and schedules of use cannot accommodate the projected 2060 SW use.
The results show that there is sufficient available SW permit capacity in the majority of the OCWP basins in 2060. That is, projected SW demands in 2060 (assuming continued use of the current supply proportions of SW and GW sources) could be fully permitted using current law and permitting protocol. Shortages in available water permits (insufficient permitted water availability for projected 2060 demands) are projected in 21 of the 82 OCWP basins across the state. The shortages begin in the first year of the analysis (2010) in 19 of these 21 basins.
2.5.4 Interstate River Compacts
The interstate river compacts Oklahoma has entered into were evaluated to assess the potential for projected water needs and water development in Oklahoma through the 50-year OCWP planning period relative to compact conditions. An interstate river compact is a formal written agreement between two or more states to divide or share the waters of a river that flows in each of the states. The compact must be approved by the legislatures of each state and approved by the U.S. Congress so that it becomes an enforceable statute in each state as well as federal law.
The benefits of entering into a compact vary between them but the overriding benefit is to provide certainty to each state on what it can do under the compact to develop and use the waters of the compacted river including future development as the increase in demand may dictate.
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Figure 2-27 –Estimated Surface Water Permit Availability Gaps in 2010
Figure 2-28 – Estimated Available Surface Water in 2060 for New Permits Section 2
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An interstate river compact also has obligations on each state as to how water may be diverted and stored for use in the state while allowing remaining flows to pass downstream to other signatory states that may also have diversion or storage provisions imposed by the compact. Often, annual accounting by a compact commission is required to determine the amount of water used under the compact and if each state complied with the compact.
Oklahoma has entered into four interstate river compacts, including two compacts on the Arkansas River; one with Kansas and one with Arkansas. It also is a signatory state with New Mexico and Texas on the Canadian River Compact, and has entered into a compact with Texas, Arkansas, and Louisiana on the Red River. Figure 2-29 depicts the river basins associated with these compacts.
Figure 2-29 –Oklahoma's Interstate River Compacts
The OCWP Water Supply Permit Availability Report discusses each of the four compacts in more detail and presents the apportionment to each state, the operation and accounting under the compact commission, the commission duties, meeting and reports, and water supply conditions, both current and possible additional uses that may be possible under the compact to meet future demand. Section 2
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Development of additional water supplies to meet current and future demand does not appear to be constrained by the four interstate river compacts in Oklahoma. Additional development in Western Oklahoma is constrained by the limited physical water supply in the Canadian River and North Canadian River due to the low precipitation, extended drought, and potential impacts of Ogallala aquifer pumping. Likewise, the potential for additional development in Southwestern Oklahoma on the Red River appears to be more limited by the water quality and by some degree to the physical supply and not by the Red River Compact.
In Central and Eastern Oklahoma, where the precipitation is greater causing more runoff and where considerable water flows into the state from Kansas and Arkansas, the compacts on the Arkansas and Red River do not impose any apparent limitations on developing additional water supply projects to meet current or future water demand. The constraint to development of additional water supply projects would appear to be more related to the water quality of the rivers, especially related to salts and TDS and the cost of removing these from the water supply by membrane treatment.