Joint Planning in Groundwater Management Area 12 Bill Hutchison, Ph.D., P.E., P.G. Director, Groundwater Resources Texas Water Development Board Lost Pines GCD Meeting November 18, 2009

Topics Overview Desired Future Condition Discussion Groundwater Budget of GMA 12 Model Run for GMA 12

Groundwater Level Decline Since Pre-Development (ft)

Groundwater Management in Texas 1904 – Rule of Capture 1949 – Groundwater Conservation Districts –Can alter, modify or discard Rule of Capture –Preferred method of groundwater management 2001 – Groundwater Management Areas –Part of SB 2

Groundwater Management Areas SB 2 (2001) –Groundwater Conservation Districts (GCD) share management plans –Joint planning (if a GCD called for it) –TWDB designated 16 GMAs

Groundwater Management Areas (GMA)

Ogallala GMA 1 & 2

Pecos Valley GMA 3

Hueco & Mesilla Bolsons GMA 5

Seymour GMA 6

Edwards- Trinity Plateau GMA 7 (3,4,9)

Trinity GMA 8, 9, 10

Edwards GMA 10 & 8

Carrizo- Wilcox GMA 11, 12, 13

Gulf Coast GMA 14, 15, 16

19 Minor Aquifers

Groundwater Management Areas HB 1763 (2005) –Annual review of management plans and accomplishments –Requires joint planning

Joint Planning GCDs within the GMA vote –1 vote per GCD Desired Future Condition Managed Available Groundwater

Groundwater Conservation Districts in Each GMA

Before HB 1763 Groundwater Availability –Groundwater Conservation Districts –Regional Water Planning Groups Groundwater Availability Models –Tools to assist in developing estimates

After HB 1763 Groundwater Availability –Desired Future Condition (DFC) –Managed Available Groundwater (MAG)

Desired Future Condition (DFC) Quantified conditions of groundwater resources Specified time or times in the future

DFC is a Broad Policy Goal Drawdown Spring flow Storage volumes

DFC vs. Other “Yield” Concepts Safe Yield Sustainable Yield

Safe Yield The amount of water which can be withdrawn from a groundwater basin annually without producing an undesired result

Sustainable Yield The amount of groundwater pumping that can be maintained for an indefinite time without causing unacceptable environmental, economic, or social consequences.

Compare and Contrast Safe Yield & Sustainable Yield –Define and Avoid Impacts DFC –Achieve a Goal

Managed Available Groundwater “Calculated” based on DFC –Texas Water Development Board Based on: –Models (including GAMs) –Water budget calculations –District provided data and information

Groundwater Availability =DFC + MAG

Groundwater Availability =DFC + MAG Policy + Science Groundwater Availability =

GROUNDWATER MANAGEMENT

“Current” Approach to Establish DFCs Define aquifers (and sometimes subunits) Define counties (and sometimes subareas) Develop individual target DFCs Define pumping estimates/constraints Define “recharge condition” (average or drought of record) Model run

“Expected” Desired Future Conditions (DFC)

“Current” Approach “Single” model run –Run model –Check drawdown against “target” DFCs –Adjust pumping –Run Model –Check drawdown against “target” DFCs –Adjust pumping :

Once Model Run is Completed MAGs calculated based on model run –Amount of pumping that will achieve DFC Split by DFC, GCD, RWPG, River Basin

Use of Central Carrizo-Wilcox GAM Historic Groundwater Budget Regional Assessment with Model Runs

Groundwater Budgets Accounting of: –Inflows –Outflows –Storage Change

Predevelopment Groundwater System

Predevelopment Groundwater System Inflow

Predevelopment Groundwater System InflowOutflow

Predevelopment Groundwater System InflowOutflow Equilibrium: Inflow = Outflow

Postdevelopment Pumping

Postdevelopment Increased Inflow Pumping

Postdevelopment Pumping Increased Inflow Decreased Outflow

Postdevelopment Increased Inflow Pumping Decreased Outflow Decreased Storage

Inflow: Precipitation GMA 13 GMA 14

Outflow: Pumping Surface Water Evapotranspiration Springs Younger Aquifers GMA 8 GMA 11 GMA 15

GMA to 1999

Dynamic Changes Due to Pumping Can be defined with modeling analysis –Increased inflow –Decreased outflow –Storage change

“Capture” ~ 500 AF/yr

“Capture” ~ 3,000 AF/yr

“Capture” ~ 50,000 AF/yr

“Capture” ~ 5,000 AF/yr

“Capture” ,000 AF/yr ??

“Capture” AF/yr ??

“Capture” ~ 500 AF/yr

“Capture” ~ 1,000 AF/yr

Pumping Increase = 64,000 AF/yr 1980 = 49,000 AF/yr 1999 = 113,000 AF/yr

Increased Inflows Inflow from GMA AF/yr Inflow from GMA 14 3,000 AF/yr Total Increased Inflow 3,500 AF/yr

Decreased Outflows Surface Water Discharge 50,000 AF/yr Spring Flow 5,000 AF/yr Evapotranspiration 0 to 10,000 AF/yr Younger Formations 500 AF/yr GMA AF/yr GMA 15 1,000 AF/yr Total Decreased Outflow 57,000 to 67,000 AF/yr

Total Capture Increased Inflow 3,500 AF/yr Decreased Outflow 57,000 to 67,000 AF/yr Total Capture 60,500 to 70,500 AF/yr

Total Capture Increased Inflow 3,500 AF/yr Decreased Outflow 57,000 to 67,000 AF/yr Total Capture 60,500 to 70,500 AF/yr Pumping Increase 64,000 AF/yr

Historic Pumping Increases Captured surface water baseflow and spring flow Decreased evapotranspiration (?) Small increases in inflows from GMA 13 and GMA 14 Small decreases in other outflows Minor storage change

Current Approach Parallel Development of –Pumping Estimates/Constraints –“Target” DFCs

“Expected” Desired Future Conditions (DFC)

Simulated Pumping (2060)

2007 SWP “Availability”

Hypothetical GMA 3 Districts 3 Aquifer (Layers) Trying to develop 9 DFCs and MAGs –Current Approach –Using groundwater model output

Regional Approach Articulate DFC as a single GMA-wide goal –Current approach averages over counties, districts (or subareas) –Equivalent to single GMA-wide average

Regional Approach MAGs - district-wide values Puts GCD management plan and rules at forefront –Permitting flexibility –Monitoring flexibility –Address “white areas”

Provide Range of Values Work with GCDs by providing useful information –Shift focus away from specific requests –Provide a broad range of estimates that should be focus of discussion (not individual projects) Apply model tools appropriately –Acknowledge model limitations –Manage expectations regarding model precision

Run GAM 7 Times Base Case –Increase 30%, 60%, 90% –Decrease 20%, 40%, 60% Plot Pumping vs. Average GMA Drawdown

URS Provided Pumping

+30 %

URS Provided Pumping +60 %

URS Provided Pumping +90 %

URS Provided Pumping - 20 %

URS Provided Pumping - 40 %

URS Provided Pumping - 60 %

Time Varying Pumping URS provided file Compare to constant pumping –Used 2060 rates

Summary Most recent pumping simulated by GMA 12 consultants increases to 268,000 AF/yr in State Water Plan “Availability” is 338,000 AF/yr

Summary GMA 12 Average Drawdown –Most recent simulation (ramped) = 83 ft –Constant pumping at 2060 levels = 90 ft –2007 SWP Availability (ramped) = 117 ft –2007 SWP Availability (constant) = 125 ft

Consider Regional Approach Articulate DFC as a single GMA-wide goal MAGs - district-wide values Puts GCD management plan and rules at forefront –Permitting flexibility –Monitoring flexibility –Addresses “white areas”

Questions? Bill Hutchison