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Intera Incorporated 1812 Centre Creek Drive, Suite 300 Austin, Texas 78754 Telephone: 512 425 2000 Fax: 512 425 2099

MEMORANDUM To:

PWPG Modeling Committee

From:

Van Kelley, INTERA Dennis Fryar, INTERA Neil Deeds, INTERA

Date:

November 11, 2009

RE:

Regional Availability and Available Supplies: Current GAM

In the planning group meeting held July 14th in Amarillo, it was determined that the draft groundwater planning numbers would be based upon the current GAM, with updated estimates being included in a later draft after the GAM is revised. In a modeling committee meeting held August 7th in Amarillo, the simulations desired by the planning group were defined. It was the intention of the group that each of these simulations be available using both the current Dutton (2004) GAM and the revised GAM being developed by INTERA. The three simulation types requested include; the Baseline Demand simulation (Baseline); the Regional Availability simulation, and the Available Supplies simulation. As defined by GMA 1, these are to be simulated using both the current GAM and the future revised GAM. Table 1 provides a summary of each of these three simulation types in terms of purpose, approach, and results. This memorandum documents the Regional Availability Simulation and the Available Supplies Simulation for the current GAM. Table 1.

Scope of simulations requested by the planning group.

Simulation Baseline (Includes updated demands)

Purpose Estimate groundwater availability with current pumping locations

Approach Use current pumping locations and projected use

Regional Availability (MAG)

Determine available groundwater given regional management goals

Available Supplies

Estimate groundwater available to each user groups

Approach employed in GAM Run 09-001 except to correct pumping annually to meet goals Refined approach to GAM Run 09-001 with management areas defined by dominant user groups

Expected Results Capability to meet demands with current infrastructure – areas of concern Theoretical availability assuming management at the one-square mile level Available supplies to be used in the needs analysis and water management strategies analysis


November 11, 2009 Page 2

Methods: The Regional Availability run and the Available Supplies run are derived from the same simulation based upon the management criteria spelled out by GMA-1 for the MAG run (Draft Run 09-001). INTERA and Freese and Nichols met with the TWDB to discuss the approach used to perform the draft MAG Run developed by the TWDB (GAM Run 09-001). The Desired Future Condition (DFC) specified by GMA-1 was: 1. 40% volume in storage remaining after fifty (50) years for Dallam, Sherman, Hartley, and Moore counties; 2. 80% volume in storage remaining after fifty (50) years in Hemphill County; 3. 50% volume in storage remaining after fifty (50) years in Hansford, Ochiltree, Lipscomb, Hutchinson, Roberts, Oldham, Potter, Carson, Gray, Wheeler, Randall, Armstrong, and Donley counties. The TWDB stated that the run was challenging to simulate and that they would like to develop an approach where pumping follows a decline curve to the target saturated thickness on a cellby-cell basis. The TWDB stated that they had a significant number of dry cells in the MAG Run (GAM Run 09-001) and that it would be better to end up in a physical state where all cells meet the target saturated thickness. As part of the work performed by INTERA to support Region A, we developed an algorithm that would calculate the flow rate in each model cell based upon a decline curve that would meet a specified target, expressed as a fraction of the initial saturated thickness. The Texas portion of the Northern Ogallala GAM was divided into three areas, each with different drawdown targets. Pumping for portions of the model in Oklahoma and New Mexico was provided by Alan Dutton. The algorithm developed for calculating regional availability used an iterative process that included MODFLOW 96 and FORTRAN utility codes that read the MODFLOW head file and calculated pumping on a yearly basis. The Northern Ogallala GAM (Dutton, 2004) was run through stress period 55 (based on Richard Smith’s GAM run 09-001 report) to provide initial water level conditions for the MAG run. Based on the stress period 55 water levels, an initial flow rate was calculated for each cell to meet the target over the 50-year horizon. These calculated flow rates were used for the first one-year MODFLOW simulation. The heads from the first one-year simulation were then used to estimate the next flow rate based upon a 49-year horizon. This process continued with one-year simulations through the 50-year timeframe. This approach, as originally contemplated, did not succeed in providing asymptotic saturated thickness declines. The reason was because of the significant hydraulic communication which could occur between model cells. A second approach was developed to ensure that pumping was sustained at rates that would accomplish the predetermined drawdown (i.e., saturated thickness). As with the first approach, the Northern Ogallala GAM (Dutton, 2004) was run through stress period 55 to provide initial water level conditions. A constant decline rate was then calculated for each model cell based on the drawdown target (fraction of initial aquifer storage remaining in 2060) for the area of the model where that cell is located.


November 11, 2009 Page 3

The calculated decline rate was used to determine a target head for each model cell on a yearly basis. This allowed for year-to-year adjustments of pumping to account for flow between cells and flow to or from boundaries. For each year, the model heads from the previous year were compared to the calculated target heads to determine the volume of water that could be removed from each cell during that year. These volumes were then combined with recharge for each cell to determine pumping rates. Figure 1 provides a hypothetical model cell pumping and head time series. In this example, the initial flow rate is calculated a priori to model simulation. However, the lower part of Figure 1 shows that the theoretical drawdown curve at the end of the first year is not achieved. This occurs because the flow rates are calculated assuming no flow from, or to, adjoining model cells. The new algorithm uses the theoretical drawdown curve to estimate the pumping rate for the next year. Through this approach, we successfully developed a method that follows the theoretical drawdown curve for each model cell closely and meets the design saturated thickness with the generation of no new inactive (dry) model cells. Results: The results determined to date include the regional groundwater availability and the available supplies for municipal and irrigation water user groups (WUGs) subject to drawdown criteria over 50 years and a pre-determined decline curve function. Results at this time are limited to the use of the existing GAM (Dutton, 2004). The drawdown criteria applied are consistent with the draft desired future conditions defined by GMA-1. This simulation differs significantly from the draft DFC/MAG simulation currently under review at the TWDB (GAM Run 09-001). Specifically, this simulation implements a consistent methodology for all regions, counties, and grid cells. Secondly, this simulation invokes the drawdown criteria at each model grid cell which implies groundwater management at the scale of one square mile. As a result, this simulation results in preservation of saturated thickness in all model grid blocks. This simulation does not increase inactive (dry) grid cells in the predictive time period. These modeling results do not take the place of the current TWDB draft DFC/MAG simulation (GAM Run 09-001) but rather augment understanding of the potential management of the resource under defined management criteria. Table 2 provides a summary of the annual regional groundwater availability by county as defined by the simulation described herein. Table 3 provides a summary of groundwater in place (storage) by county from the simulation described herein. This estimate of storage accounts for the variable specific yield implemented in the GAM. By dividing the 2060 groundwater in place by the 2010 groundwater in place and multiplying by 100 one should calculate the management criterion applied to that county minus round off. For the available supplies by WUG we analyzed the two largest WUGs, irrigation and municipal. To perform these calculations required definition of WUG zones for both categories within the model area. This required assignment of specific grid cells of the model with pumping associated with these two WUGs. A single cell could not be assigned multiple WUGs. Figure 2 provides the coverage of the irrigation zones used and Figure 3 provides the coverage of the municipal zones used. Each irrigation WUG zone was tracked by WUG type, county, river


November 11, 2009 Page 4

basin, and groundwater conservation district. Each municipal WUG zones was tracked by WUG type, county, river basin, and municipality. This approach resulted in 26 unique irrigation zones and 35 unique municipal zones. Table 4 provides the available irrigation supply by county and Table 5 provides the available municipal supply by county. One will note that in tables 4 and 5 the year 2011 has been added to the table in addition to the typical decadal reporting convention. The reason for this is that the initial pumping rate calculated for the year 2010 was typically an underestimate of the true rate required to attain the drawdown calculated for that one year time period. As a result, the algorithm developed corrected that rate in the next year of simulation to account for the communication between model cells. From that simulation year forward the flow rate was calculated specifically to attain a theoretical drawdown curve (see Figure 1). Generally after the year 2011 the flow rates were on a downward trend from 2012 through 2060. References: Dutton, A., 2004. Adjustments of Parameters to Improve the Calibration of the Og-n Model of the Ogallala Aquifer, Panhandle Water Planning Group, Prepared for Freese and Nichols, Inc. and the Panhandle Water Planning Group, June 2004.


November 11, 2009 Page 5

Table 2. County Armstrong Carson Dallam Donley Gray Hansford Hartley Hemphill Hutchinson Lipscomb Moore Ochiltree Oldham Potter Randall Roberts Sherman Wheeler Sum

Table 3. County Armstrong Carson Dallam Donley Gray Hansford Hartley Hemphill Hutchinson Lipscomb Moore Ochiltree Oldham Potter Randall Roberts Sherman Wheeler Sum

Annual regional groundwater availability - AFY. 2010 48,916 198,232 290,088 90,450 186,939 279,085 413,782 82,951 153,829 260,989 172,388 257,903 5,288 38,084 19,730 375,334 316,971 120,205 3,311,163

2020 40,834 178,545 253,072 81,347 157,029 258,780 361,195 44,654 129,548 253,488 164,319 236,618 6,434 29,224 18,411 339,518 298,567 114,819 2,966,401

2030 36,089 160,493 225,124 76,005 143,819 238,529 314,995 44,129 119,798 247,761 142,529 215,489 6,090 26,093 16,419 322,909 262,820 112,163 2,711,253

2040 31,978 144,656 198,739 69,672 130,646 217,640 273,474 43,784 108,985 234,999 122,138 195,506 5,571 23,205 14,589 301,420 229,557 106,500 2,453,060

2050 28,462 129,882 173,986 63,613 117,614 195,835 236,815 43,673 98,239 219,735 103,539 176,566 5,079 20,684 12,974 277,509 198,809 99,802 2,202,815

2060 25,383 116,336 151,305 58,017 105,634 174,892 204,661 43,579 87,979 203,198 86,974 159,017 4,658 18,459 11,531 251,933 169,672 92,993 1,966,221

2050 2,007,702 8,489,527 7,596,070 3,453,986 7,618,601 11,879,677 11,603,668 12,947,908 6,087,234 10,873,857 4,540,089 11,083,298 141,974 1,550,482 876,866 15,657,191 8,860,604 4,369,708 129,638,441

2060 1,757,463 7,367,135 6,270,784 3,021,052 6,621,642 10,213,135 9,725,660 12,352,238 5,257,916 9,477,201 3,714,338 9,580,902 124,384 1,353,520 771,861 13,557,937 7,320,539 3,824,747 112,312,455

Groundwater in place – AFY. 2010 3,393,836 14,523,374 15,651,329 5,822,805 13,000,446 20,769,174 23,097,231 15,407,023 10,542,798 18,394,426 9,608,708 19,066,318 238,603 2,632,774 1,455,665 26,852,172 18,035,001 7,340,143 225,831,824

2020 2,980,888 12,748,607 13,171,909 5,121,980 11,420,486 18,218,902 19,495,348 14,834,800 9,248,736 16,186,671 8,053,014 16,739,260 210,149 2,311,941 1,283,475 23,590,451 15,203,063 6,468,071 197,287,750

2030 2,614,958 11,166,494 11,022,071 4,498,266 10,008,063 15,883,250 16,428,918 14,206,672 8,078,744 14,214,079 6,694,926 14,648,686 184,496 2,026,885 1,131,174 20,655,707 12,766,854 5,684,345 171,914,589

2040 2,292,115 9,751,901 9,172,190 3,944,520 8,744,601 13,768,737 13,820,010 13,569,550 7,025,960 12,448,522 5,528,205 12,768,510 161,908 1,774,128 996,195 18,018,243 10,667,622 4,987,318 149,440,235


November 11, 2009 Page 6

Table 4. County Armstrong Carson Dallam Donley Gray Hansford Hartley Hemphill Hutchinson Lipscomb Moore Ochiltree Potter Randall Roberts Sherman Wheeler

Table 5. County Armstrong Carson Dallam Donley Gray Hansford Hartley Hemphill Hutchinson Lipscomb Moore Ochiltree Potter Randall Roberts Sherman Wheeler

Available irrigation supplies by county (AFY). 2010 4,863 99,376 122,148 28,483 39,434 91,195 102,548 1,983 27,517 27,284 65,363 57,568 1,788 4,104 21,838 121,224 10,429

2011 6,639 109,908 151,907 32,927 46,544 117,316 113,191 2,222 27,621 32,719 80,586 72,556 3,131 6,390 30,043 147,808 12,558

2020 5,767 101,110 135,104 30,629 43,347 114,936 101,126 2,492 27,921 34,005 72,212 67,470 2,469 4,857 27,084 131,122 12,818

2030 5,051 92,086 118,797 28,611 40,598 109,261 89,569 2,843 27,126 33,214 64,505 63,162 1,929 4,356 24,314 114,716 12,440

2040 4,477 83,796 103,857 26,626 37,676 101,068 78,674 3,000 25,605 31,947 56,716 58,444 1,555 3,918 21,889 99,927 11,961

2050 3,962 75,773 90,356 24,638 34,463 90,839 68,550 2,997 23,581 30,360 48,993 53,619 1,290 3,495 19,460 86,586 11,309

2060 3,511 67,954 77,787 22,617 31,290 80,500 59,098 3,032 21,394 28,479 41,407 48,921 1,065 3,080 17,005 74,048 10,537

Available municipal supplies by county (AFY). 2010 443 9,252 1,841 255 2,040 2,768 2,066 238 1,326 2,710 2,253 2,494 3,478 1,819 16,531 1,591 2,304

2011 663 18,294 2,068 248 2,361 2,842 3,033 377 4,443 3,277 2,898 3,625 2,576 4,174 31,742 1,894 2,579

2020 591 15,707 2,321 239 1,562 1,678 2,550 354 3,655 3,749 2,155 3,634 2,759 2,748 29,155 1,835 2,476

2030 528 14,025 2,483 214 1,152 1,399 2,045 356 3,130 4,056 1,693 3,604 2,787 2,173 27,733 1,680 2,287

2040 471 12,481 2,477 194 768 1,121 1,606 372 2,693 4,125 1,306 3,611 2,660 1,775 26,200 1,460 2,025

2050 420 11,090 2,357 176 624 1,018 1,231 386 2,316 4,047 1,007 3,478 2,457 1,498 24,283 1,249 1,725

2060 374 9,957 2,182 161 541 1,004 965 399 1,989 3,885 737 3,238 2,261 1,274 22,274 1,085 1,444


November 11, 2009 Page 7

Figure 1.

Approach to developing flow rates in the regional availability simulation.


November 11, 2009 Page 8

Irrigation Zones Texhoma

U8 7

S15

OCHILTREE

LIPSCOMB

Spearman

U287

4 U5

S102

U83

HANSFORD Gruver

SHERMAN

S70

DALLAM

Booker Darrouzett

Dalhart

S213

Higgins

S51

Morse

Cactus

Follett S15

Perryton

S305

U385

Stratford

S207

Texline

S2 07

Sunray

Canadian Dumas S152 85 U3

ROBERTS

Sanford

S354

Fritch

Miami

CARSON

Pampa

6 S335 13 S I40 B Amarillo

McLean

Groom

S207

Howardwick

DONLEY Clarendon S70

CASTRO

I40

S70

I27

RANDALL

ARMSTRONG

PARMER

SWISHER

BRISCOE

COLLINGSWORTH

3 S20 Hedley

HALL

CHILDRESS 0

BAILEY

LAMB

S152

WHEELER

S273

U2 87 Claude

Lake Tanglewood Lake Tanglewood

DEAF SMITH

Wheeler

GRAY

Panhandle

I40

Mobeetie

S2 73 Lefors

0 U6 White Deer

S207

87 U

POTTER

S33

Borger Skellytown

OLDHAM

HEMPHILL U83

Channing

HUTCHINSON Stinnett

MOORE

S2 73

HARTLEY

HALE

FLOYD

MOTLEY

10

20 HARDEMA

Miles COTTLE FOARD

Irrigation Zones

IRR-HANSFORD-NPGCD-CanadianRB

IRR-POTTER-PGCD-CanadianRB

IRR-ARMSTRONG-PGCD-RedRB

IRR-HARTLEY-NPGCD-CanadianRB

IRR-POTTER-PGCD-RedRB

IRR-CARSON-PGCD-CanadianRB

IRR-HEMPHILL-HemphillGCD-CanadianRB

IRR-RANDALL-HighPlainsGCD-RedRB

IRR-CARSON-PGCD-RedRB

IRR-HUTCHINSON-NPGCD-CanadianRB

IRR-RANDALL-noGCD-RedRB

IRR-DALLAM-NPGCD-CanadianRB

IRR-HUTCHINSON-noGCD-CanadianRB

IRR-ROBERTS-PGCD-CanadianRB

IRR-DALLAM-noGCD-CanadianRB

IRR-LIPSCOMB-NPGCD-CanadianRB

IRR-ROBERTS-PGCD-RedRB

IRR-DONLEY-PGCD-RedRB

IRR-MOORE-NPGCD-CanadianRB

IRR-SHERMAN-NPGCD-CanadianRB

IRR-GRAY-PGCD-CanadianRB

IRR-OCHILTREE-NPGCD-CanadianRB

IRR-WHEELER-PGCD-RedRB

IRR-GRAY-PGCD-RedRB

IRR-POTTER-HighPlainsGCD-RedRB

IRR-HEMPHILL-HemphillGCD-REDRB

Figure 2. Irrigation zones for available supplies calculations.


November 11, 2009 Page 9

Municipal Zones

Texhoma

SHERMAN

Morse

Cactus

Borger

S152

Stinnett

ROBERTS

TCW Supply

Miami

Borger

CRMWA

Fritch

Skellytown Hi Texas Water Co.

Wheeler

Lefors

S152

S207

DONLEY

I40

Howardwick U2 87

ARMSTRONG

Clarendon S70

RANDALL

Shamrock

McLean

S70

Claude

Lake Tanglewood

GRAY

Groom

S2 73

S207

U87

Panhandle

CARSON

S335

36 S1

I27

I40

DEAF SMITH

WHEELER Mobeetie

S2 73

S273

I40 B

Amarillo

White Deer

7 U8

POTTER

Pampa 0 U6

City of Amarillo

OLDHAM

S33

U83

Sanford Fritch

Canadian

HEMPHILL

6 S13

85 U3

S354

Higgins

HUTCHINSON

MOORE

Channing

S213

S51 S2 07

Sunray

Dumas Dumas

LIPSCOMB

S70

Dalhart

HARTLEY

OCHILTREE Spearman

U287

4 U5

Perryton

HANSFORD Gruver

S305

S15

S171

U385

Stratford

U8 7

Follett S15

Booker

U83

DALLAM

S102

S23 Darrouzett

S207

Texline

COLLINGSWORTH

Hedley Memphis

PARMER

CASTRO

SWISHER

BRISCOE

HALL

−

CHILDRESS

0

10

Miles

Figure 3. Municipal zones for available supplies calculations.

20


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