The Role of Modeled Available The Role of Modeled Available The Role of Modeled Available The Role of Modeled Available

Groundwater in Local Regulation Groundwater in Local Regulation Groundwater in Local Regulation Groundwater in Local Regulation

and State Planning and State Planning and State Planning and State Planning and State Planning and State Planning and State Planning and State Planning

Presented By Bill Mullican, PG.,to the

2015 Texas Alliance of Groundwater DistrictsGroundwater Summit

San Marcos, Texas

99

How many major

aquifers have

been designated been designated

in Texas?

199,000,000,000,000,001199,000,000,000,000,001

According to a recent

scientific study published by

Johnson, McCarthy, and

Jones, what is the volume of Jones, what is the volume of

groundwater, in AFY,

available in Texas today?

66

How many acronyms using the letters A, G,

and M can be utilized based on TWC Chapter

36?

GAM – Groundwater Availability Model

GMA – Groundwater Management Area

MAG – Modeled Available GroundwaterMAG – Modeled Available Groundwater

MGA – Modeled Groundwater Applications

AGM – Approved Groundwater Model, and

AMG – Attorneys for Modeled Groundwater

16 Planning Regions16 Planning Regions

Three Texas Water Plans Published since SB 1 in 1997Three Texas Water Plans Published since SB 1 in 1997Six prior to SB 1 (1961, 1968, 1984, 1990, 1992, and 1997)Six prior to SB 1 (1961, 1968, 1984, 1990, 1992, and 1997)

11

Texas Water Code Chapter 16.053 (e) & (2-a)

(e) Each regional water planning group shall submit to the

development board a regional water plan that:

(2-a) is consistent with the desired future conditions adopted

under Section 36.108 for the relevant aquifers located in the under Section 36.108 for the relevant aquifers located in the

regional water planning area as of the date the board most

recently adopted a state water plan under Section 16.051 or, at

the option of the regional water planning group, established

subsequent to the adoption of the most recent plan.

31 Texas Administrative Code Chapter 357.32 (d)

RWPGs shall use modeled available groundwater volumes for

groundwater availability, as issued by the Board, and incorporate

such information in its RWP unless no modeled available

groundwater volumes are provided. Groundwater availability groundwater volumes are provided. Groundwater availability

used in the RWP must be consistent with the desired future

conditions as of the date the Board most recently adopted a

state water plan or, at the discretion of the RWPG, established

subsequent to the adoption of the most recent state water plan.

8,000

10,000

12,000

Scenario 1 - Drought Demands vs. MAGS

Drought Water Demand

Average Historical Use

0

2,000

4,000

6,000

1 2 3 4 5 6 7 8 9 10

Years

8,000

10,000

12,000

Scenario 2 - Pumping + New Strategy

vs. MAG

MAG = 10,000 AFY • Pumping in Year 1

starts at 5,500 AFY

and increases at a

rate of 100 AFY for

50 years

• WMS = 1,000 AFY

0

2,000

4,000

6,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

Pumping Strategy

• WMS = 1,000 AFY

pumping starting in

Year 1

• MAG = 10,000 AFY

• Total pumping +

WMS =447,500

• Excess MAG =

47,500 AF.

400,000

500,000

600,000

Scenario 2 - Cumulative MAG vs

Cumulative Pumping + WMS

0

100,000

200,000

300,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

Cumulative MAG Cumulative Pumping + WMS