Management Application:

Volume of Water in Storage

(An Ogallala Example with Applicability to All Aquifers in Texas)

Judy A. Reeves, Ph.D. Hydrogeologist, High Plains Water District

Ken Rainwater, Ph.D., P.E., DEEDirector, Water Resources Center

Texas Tech University

Storage Volumes: Calculation Methods

Planimeter method Mass balance GIS MODFLOW (or other) models GAM model with GIS

Texas Tech Modflow Model Pre-GAM model for Region O Contract stipulated high calibration

standards, variable Sy

Emphasized distribution of pumping and irrigation return flow (IRF)

High recharge values attributed to IRF Reported unmet demands Dry cell problem

LERWPG"Cedar Pencil Model"

GAM03-22

GAM04-05

Mass Balance 04-07

BaselineDrought

(start 2015)

1995 4,753,000 4,753,000 3,539,374 3,539,3741996 5,136,990 3,293,5531997 3,070,7231998 2,860,9211999 2,694,3932000 4,811,000 4,811,000 3,539,374 2,556,5562001 2,424,4172002 2,297,9812003 4,811,458 2,177,2452004 4,776,421 5,480,511 2,062,2122005 4,741,766 1,952,8792006 4,707,357 1,849,2492007 4,673,273 1,751,3202008 4,639,345 1,659,0932009 4,605,889 1,572,5672010 4,893,000 4,893,000 3,539,374 4,572,867 4,993,208 1,077,0872011 4,540,308 966,8222012 4,508,423 917,1162013 4,477,057 837,9692020 5,108,000 4,744,000 3,539,374 4,432,736 299,5912025 Out of water2030 5,347,000 4,991,000 3,539,374 3,965,4262040 5,645,000 4,990,000 3,539,374 3,615,2472050 5,975,000 5,342,000 3,539,374 3,591,1072060 3,533,107

Volume of Groundwater in Storage in County "A"(acre-feet)

TTU Model

LERWPG “Cedar Pencil Model”

Areas between contour lines on saturated thickness map by planimeter

Multiplied area by mean saturated thickness, Sy = 0.15

Accurate for year mapped Unable to project into the future

LERWPG"Cedar Pencil Model"

GAM03-22

GAM04-05

Mass Balance 04-07

BaselineDrought

(start 2015)

1995 4,753,000 4,753,000 3,539,374 3,539,3741996 5,136,990 3,293,5531997 3,070,7231998 2,860,9211999 2,694,3932000 4,811,000 4,811,000 3,539,374 2,556,5562001 2,424,4172002 2,297,9812003 4,811,458 2,177,2452004 4,776,421 5,480,511 2,062,2122005 4,741,766 1,952,8792006 4,707,357 1,849,2492007 4,673,273 1,751,3202008 4,639,345 1,659,0932009 4,605,889 1,572,5672010 4,893,000 4,893,000 3,539,374 4,572,867 4,993,208 1,077,0872011 4,540,308 966,8222012 4,508,423 917,1162013 4,477,057 837,9692020 5,108,000 4,744,000 3,539,374 4,432,736 299,5912025 Out of water2030 5,347,000 4,991,000 3,539,374 3,965,4262040 5,645,000 4,990,000 3,539,374 3,615,2472050 5,975,000 5,342,000 3,539,374 3,591,1072060 3,533,107

Volume of Groundwater in Storage in County "A"(acre-feet)

TTU Model

GAM Run 03-22 Steady-state model

Predevelopment conditions (1940) Calibrate hydraulic conductivity and recharge

Transient model Built on steady-state calibration Uniform pumping distribution on irrigated

lands Refined calibration mainly through enhanced

recharge (both irrigated and nonirrigated lands)

Margins of model domain have many dry or flooded cells

LERWPG"Cedar Pencil Model"

GAM03-22

GAM04-05

Mass Balance 04-07

BaselineDrought

(start 2015)

1995 4,753,000 4,753,000 3,539,374 3,539,3741996 5,136,990 3,293,5531997 3,070,7231998 2,860,9211999 2,694,3932000 4,811,000 4,811,000 3,539,374 2,556,5562001 2,424,4172002 2,297,9812003 4,811,458 2,177,2452004 4,776,421 5,480,511 2,062,2122005 4,741,766 1,952,8792006 4,707,357 1,849,2492007 4,673,273 1,751,3202008 4,639,345 1,659,0932009 4,605,889 1,572,5672010 4,893,000 4,893,000 3,539,374 4,572,867 4,993,208 1,077,0872011 4,540,308 966,8222012 4,508,423 917,1162013 4,477,057 837,9692020 5,108,000 4,744,000 3,539,374 4,432,736 299,5912025 Out of water2030 5,347,000 4,991,000 3,539,374 3,965,4262040 5,645,000 4,990,000 3,539,374 3,615,2472050 5,975,000 5,342,000 3,539,374 3,591,1072060 3,533,107

Volume of Groundwater in Storage in County "A"(acre-feet)

TTU Model

GAM Run 04-05

Used new demand numbers approved by the TWDB in Sept 2003

No recalibration of previous GAM model

LERWPG"Cedar Pencil Model"

GAM03-22

GAM04-05

Mass Balance 04-07

BaselineDrought

(start 2015)

1995 4,753,000 4,753,000 3,539,374 3,539,3741996 5,136,990 3,293,5531997 3,070,7231998 2,860,9211999 2,694,3932000 4,811,000 4,811,000 3,539,374 2,556,5562001 2,424,4172002 2,297,9812003 4,811,458 2,177,2452004 4,776,421 5,480,511 2,062,2122005 4,741,766 1,952,8792006 4,707,357 1,849,2492007 4,673,273 1,751,3202008 4,639,345 1,659,0932009 4,605,889 1,572,5672010 4,893,000 4,893,000 3,539,374 4,572,867 4,993,208 1,077,0872011 4,540,308 966,8222012 4,508,423 917,1162013 4,477,057 837,9692020 5,108,000 4,744,000 3,539,374 4,432,736 299,5912025 Out of water2030 5,347,000 4,991,000 3,539,374 3,965,4262040 5,645,000 4,990,000 3,539,374 3,615,2472050 5,975,000 5,342,000 3,539,374 3,591,1072060 3,533,107

Volume of Groundwater in Storage in County "A"(acre-feet)

TTU Model

Mass Balance

Not a hydrologic model Annual volumetric calculations

Begin with initial storage volume Subtract new demand volumes Add average recharge

LERWPG"Cedar Pencil Model"

GAM03-22

GAM04-05

Mass Balance 04-07

BaselineDrought

(start 2015)

1995 4,753,000 4,753,000 3,539,374 3,539,3741996 5,136,990 3,293,5531997 3,070,7231998 2,860,9211999 2,694,3932000 4,811,000 4,811,000 3,539,374 2,556,5562001 2,424,4172002 2,297,9812003 4,811,458 2,177,2452004 4,776,421 5,480,511 2,062,2122005 4,741,766 1,952,8792006 4,707,357 1,849,2492007 4,673,273 1,751,3202008 4,639,345 1,659,0932009 4,605,889 1,572,5672010 4,893,000 4,893,000 3,539,374 4,572,867 4,993,208 1,077,0872011 4,540,308 966,8222012 4,508,423 917,1162013 4,477,057 837,9692020 5,108,000 4,744,000 3,539,374 4,432,736 299,5912025 Out of water2030 5,347,000 4,991,000 3,539,374 3,965,4262040 5,645,000 4,990,000 3,539,374 3,615,2472050 5,975,000 5,342,000 3,539,374 3,591,1072060 3,533,107

Volume of Groundwater in Storage in County "A"(acre-feet)

TTU Model

Trend Analysis: Volume of Water in Storage

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

Year

Acre

-Feet

GAM 03-22

TTU Baseline

TTU Drought

LERWPG CedarPencil

GAM 04-05

Mass Balance 04-07

Water managers selling volumes to their constituents ….

Data Gaps

Recharge Pump distribution Specific yield Base of aquifer

Recharge Issues Predevelopment or without cultivation

Regional values <0.5 in/yr Playa lakes focus recharge

Model calibration Pre-GAM model for 1985-95

<0.5 in/yr in uncultivated lands Average 2.75 in/yr in irrigated, cultivated lands Also calibrated pumpage distribution

GAM runs Calibrated recharge, but not pumpage distribution

Recharge Issues Need for field observations

Know Winter depth to water (-> saturated

thickness) Crop patterns

Need Local withdrawal estimates Local precipitation measurements

Find Combination of recharge and IRF

Pumping Distribution Greatest uncertainty in planning

process Irrigation estimates for maximum yield

tend to be much larger than actual Metering underway in several

conservation districts Some IRF needed to flush salts Withdrawal will cease when saturated

thickness gets too small

Specific Yield Original estimates from Knowles et al.

(1984) field and modeling work Range 0.08 < Sy < 0.24 Relatively insensitive for head

calibration over long periods Directly proportional to storage

volume Can be refined if recharge, IRF, and

withdrawals are precise

Base of Aquifer Map

Thousands of well logs for dataset Occasional debate about pick for

aquifer bottom Ogallala/Cretaceous Ogallala/Dockum

GIS tools allow easier review of data Bottom topography affects flow

Conclusions Groundwater management plans

accept uncertainties Uncertainties can be tested and

refined with modern modeling techniques

Model results must be compared to real data

Real data drive refinement of the modeling tools

Recommendations

Local involvement with process Local districts and landowners are

closest to local storage and production data

Large production areas can be broken down into understandable pieces

Interaction with modelers Critical review of model results Refinement of calibrated parameters