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Surface Water Availability. Surface Water Considerations

Mar 29, 2015



  • Slide 1

Surface Water Availability Slide 2 Surface Water Considerations Slide 3 Excess Surface Water 25% of water available on an average, annual basis above that required to meet existing/projected future needs, for non-riparian uses or interbasin transfer. Existing/Projected Needs: 1. Existing riparian rights 2. Water needs of federal water projects 3. Firm yield of reservoirs 4. Maintenance of instream flows (Fish & Wildlife, WQ, Navigation, and Aquifer Recharge), and 5. Future needs in that basin Slide 4 Excess Surface Water Determination 1990 Plan calculated excess water for 8 areas using 19 gages 2014 Update uses 51 gages to calculate excess water in 9 major river basins and 32 sub-basins Updated stream flow data and demands No change assumed if demand decreased Slide 5 Slide 6 Excess Water, by River Basin River Basin Excess Water (Million ac-ft/yr) White River (Cache)1.7 Arkansas River3.3 Delta1.6 Ouachita River1.0 Red River1.1 Slide 7 Excess Surface Water Availability Results 1990 Statewide total excess surface water ~10.5 million ac-ft Updated Statewide total ~8.74 million ac-ft Differences result from updated demand projections, changes in in-stream needs (e.g., White River minimum flows), and basin differences (e.g., 1990 East Arkansas methodology) Represents annual average, but does not reflect seasonal variations Slide 8 US Army Corps of Engineers (USACE) Projects Arkansas Water Plan (AWP) references the annual summary of USACE projects Current allocation status for each reservoir Summary of general process required for reallocation Slide 9 Slide 10 Interstate Compacts Compact delivery requirements limit available surface water Arkansas River Compact (AR and OK) Red River Compact (OK, TX, AR and LA) includes all areas south of the Arkansas River watershed Slide 11 Fish and Wildlife Flows Slide 12 Subgroup formed Technical workshop March 2013 Reviewed the Arkansas Method, Modified Tennant Method Reviewed national and southeastern methods for estimating instream flows Recommended path forward Slide 13 Recommendations Use the Arkansas Method for estimating fish and wildlife flows and updating excess flow estimates for the 2014 Arkansas Water Plan Determine flow-ecology relationships and develop an empirical, risk-based method for estimating flow-ecology (e.g., fishery) relationships, based on: Magnitude Frequency Duration Timing, and Rate of change of flow Slide 14 Recommendations (Continued) Framework for adopting alternative methods for F&W flows into Arkansas Water Plan (i.e., adaptive management), which requires: 1. Defining how flows were determined (e.g., USGS gauge) 2. Specifying the applicable stream classes (e.g. extraordinary resource waters) 3. Documenting the current hydrologic status 4. Confirming the flow-ecology relationships are scientifically defensible 5. Documenting the stakeholder process used to refine, if needed, flows to achieve all designated uses 6. Monitoring and periodically assessing flow-ecology relations Slide 15 Recommendations (Continued) Propose approaches for reducing the likelihood of declared water shortages and stopping withdrawals For Illustration Only Slide 16 Surface Water Quality Surface Water Quality Slide 17 Information Sources State-wide information sources ADEQ USGS Updated information since 1990 Plan Selected sources within water resources planning regions Beaver Water District Ft. Smith Central Arkansas Water ANRC AR Department of Health Slide 18 Analyses Used existing results for current status 305(b) reports 303(d) lists Demand water use sectors Summary by AR WR Planning Regions WQ Trend analyses at concurrent water supply sites Flow-adjusted Seasonal Kendall trend analyses Issues: since 1990 Plan and emerging Slide 19 Current (2008) Water Quality: Impaired Stream Miles, Lake Acreage Designated use Water Demand Sector Use Impaired Stream Miles/% of Total Assessed Impaired Lake Acres/% of Total Assessed Fish ConsumptionRecreation 363.3/3%23,637/6% Aquatic LifeFish & Wildlife 2,439.9/25%11,248/3% Primary ContactRecreation 564.8/6%0 Secondary ContactRecreation 7/0.01%0 Domestic Water SupplyDrinking Water 448.3/4%97,105/27% Ag & Industrial Water SupplyAgriculture, Industry 967.7/10%0 Total miles (acres) impaired 4,086.5/41%127,520/36% Total miles (acres) assessed 9,849.7357,896 Slide 20 Causes of Impairment (2008) CausesStream MilesLake Acres Siltation/Turbidity1,156.33,235 Organic Enrichment/ Low DO/Nutrients 1,3084,625 Mercury31918,677 Priority Organics44.8