An Interregional Water Solution with Conjunctive Use of Groundwater

An Interregional Water Solution with Conjunctive Use of Groundwater Haskell L. Simon President, Coastal Plains Groundwater Conservation District Vice President, Region K Water Planning Group

SB1 (1997)Mandate for Statewide Water Plan • New Era for Water Planning Based on “Bottom Up” or “Grass Roots” Approach • Address anticipated water shortages over a 50 year period by determining: • Available water supplies • Demands for water • Strategies to achieve projected short falls

The Essence of the SB1 Process Today Before Bottom Up Approach Top Down Approach vs.

SB1 Regional Approach • 16 Regions in Texas • Each group represented by one or more individuals from 11 “Interest Groups” • RWPG is responsible for preparing and adopting a regional water plan • Regional Plans consolidated into the State Water Plan “Water for Texas 2002” • Implementation of the Plan will require legislative and/or regulatory action.

Regional Water Planning Areas

Public Counties Municipalities Agricultural Interests Environmental Interests Industries Small businesses River Authorities Water Districts Water Utilities Electrical Generating Utilities Regional Planning Group Membership(11 Interest Groups)

Million Acre-feet Year Projected Urban & Agricultural Water Uses

Total Water Demand by Type of Use (2003) Year 2060 Year 2000

Use by Source of Supply (2000) GROUND- WATER 35% SURFACE WATER 65%

SB 1 Planning Process (entire state & border regions) Region K 2050 Water Needs • 2050 Shortfalls • 160,000 acre-feet/yr of irrigation • Some rural communities upstream of • Highland Lakes (5,400 acre-feet/yr)

SB 1 Planning Process (entire state & border regions) 2050 Water Needs Region L • Bexar County shortfall • 350,000 acre-feet/yr of municipal use • (current update to plan will reduce this amount)

SB 1 Planning Process (entire state & border regions) Region L (SAWS) Region K (LCRA) Regional Cooperation Defines Project LCRA-SAWS Water Project

Regional sharing of resources to meet future water needs • The LCRA-SAWS Water Project is designed to meet the needs of both the lower Colorado River basin and the San Antonio area • The lower Colorado River basin needs additional water to satisfy agricultural needs, protect Highland Lake levels and provide water for upstream rural communities • San Antonio needs significant additional water to meet growth and economic development needs

Project Summary • Construct off-channel reservoirs to store surface waters • Institute practices and improvements to reduce agriculture’s demand for water • Install groundwater wells to serve agriculture’s needs during drought • Create up to 150,000 acre-feet per year for SAWS • Meet environmental requirements • Study Period activities determine implementability and permitting

Water for San Antonio (up to 150,000 ac-ft/yr) LCRA-SAWS Water Project Water for rural communities More stable water levels in Highland Lakes Lake Buchanan Austin Instream flows to maintain aquatic habitat San Antonio Water for agriculture Freshwater inflows for Matagorda Bay

2. Off-channel reservoirs 3. Conjunctive use of groundwater for agricultural needs during drought P P LCRA SAWS Water Project Colorado Develop 330,000 ac-ft of water by: 1. Irrigation conservation • Onsite and system improvements in districts Columbus Wharton Wharton Matagorda Bay City Matagorda Bay

Legislation requires that in order for the project to proceed, the project must ... • Protect and benefit basin interests • Be consistent with the state regional water plan • Provide inflows adequate to maintain the ecological health and productivity of Matagorda Bay • Maintain current instream river flow protections • Ensure that San Antonio practices stringent conservation measures • Provide for a broad public and scientific review process • Benefit stored water levels in Lakes Travis and Buchanan

We are at the beginning of a multi-year, comprehensive evaluation Permitting Review & Completion of Studies Permit Submittal & Continuation of Studies Technical Study Plan Development Technical Studies 2002 2004 2010 2007-2008

Groundwater • Average of 62,000 ac-ft per year in severe droughts • Divert only to Colorado basin agricultural users • Groundwater used only in times of drought

Groundwater Modeling Overview • Simulate a range of withdrawals to meet agricultural needs during drought • Evaluate impacts to groundwater/ surface water • Assess impacts of pumping on groundwater quality • Assess uncertainty with model predictions

Groundwater Study Objectives • Potential mitigation techniques for users, if affected • Saline water encroachment from the coast. • Land surface subsidence • Induced migration of poor quality native groundwater that could result from increased groundwater use Determine if additional groundwater can be developed without substantially affecting the current groundwater users and evaluate:

Comprehensive Groundwater Evaluation • Defines consequences of conjunctive use • Identifies mitigation needs and options • Uses more data and performs more data analyses than the GAM • Predictions will contain confidence limits based on uncertainty associated in calibrated model • Model will be developed at the spatial resolution supported by the data • 0.1 to 0.5 mile variable grid anticipated

Stay tuned . . .

An Interregional Water Solution with Conjunctive Use of Groundwater