Serving Lincoln County for more than a century!
Serving Lincoln County for more than a century!
With completion of the GWMA groundwater model, identifying solutions begins with the launch of two new modeling projects to assess municipal groundwater supplies and identify sustainable wells along the east low canal.
For the past two years, the Columbia Basin Ground Water Management Area (GWMA) has been developing a sophisticated computational groundwater model of the four Columbia Basin counties. This year the state appropriated $1.0 million for GWMA “to use the model to help answer critical questions about groundwater supply, recharge and aquifer storage,” according to Paul Stoker, GWMA executivedirector.
In describing the municipal water supply assessment modeling at the GWMA administrative board meeting recently at Othello City Hall, Stoker said, “These assessments will simulate aquifer water budgets to allow evaluation of each community’s long-term water supply outlook. The assessment project will also evaluate the need for, and scope of, potential deep-well injection – aquifer storage and recovery – projects that could reverse, or at least stabilize, the decline in local water levels.”
Regarding the identification of sustainable wells along the east low canal, hydrogeologist Dr. Kevin Lindsey, GSI Water Solutions, Inc. (GSI), explained how GWMA scientists “will test wells and develop model simulations of the potential impacts of recharge from alluvial systems on irrigation wells near the canal to identify wells that are, and are not, in hydrologic connection with the alluvial and canal systems.”
Stoker noted that the sustainability project originated during discussions with the Bureau of Reclamation on the agency’s interest in identifying wells that may not need surface water supply replacement due to a history of groundwater recharge from shallow water sources. “This project will improve the decision-making for the Odessa Special Study by increasing the number of acres currently receiving rechargeable water,” he said.
Also at the GWMA administrative board meeting, board members and the attending public listened and watched as GWMA scientists and staff presented the final report on the GWMA Groundwater Hydrologic Modeling Project, focusing on the future value of the three-dimensional (3D) groundwater simulation tool in supporting local, state and federal decision-making.
“We know the aquifer is mostly ancient water and declining. The good news is, we now have a specialized tool that can assess groundwater supply conditions by sub-region, and provide us with reliable information for future decision-making,” said Lincoln County Commissioner Dennis Bly.
In describing the Hydrologic Modeling Project, Lindsey said it was “designed to help identify the locations, mechanisms and rates of groundwater recharge and discharge. The over-arching objective was to develop a quantitative tool for describing the groundwater system by sufficiently simulating the hydrologic processes. The model will enable GWMA to evaluate historic and current impacts to the groundwater system from development and support future water resource management projects and decisions, as is planned with the municipal water-supply assessments over the next 12 months.”
Remarking on the groundwater model’s potential, Lincoln County Commissioner Scott Hutsell said, “The groundwater model will be essential for further evaluation of groundwater sub-regions, and to support analyses of alternative resource management options, which will move forward this year with the passive rehydration project and, importantly, help determine water supply options for the towns and cities of Lincoln County, most of which are facing difficult times ahead.”
Stoker explained that the model is constructed to recognize the fact that the GWMA lies within a multiple-state hydrologic setting that extends into both Idaho and Oregon. The GWMA modeling approach includes two models: one that simulates conditions only within the GWMA (the GWMA Model), and a model that simulates conditions throughout the entire Columbia Plateau aquifer (the Watershed Model). The Watershed Model ensures that calculations made using the GWMA Model are constrained by and consistent with the overall regional groundwater budget. Model development has been conducted under a GWMA contract by GSI Water Solutions, Inc. and S.S. Papadopulos & Associates, Inc.
To date, the following important inferences have been drawn from the model:
• The model displays the effects that geologic structures underground have on groundwater movement. These structures provide barriers to groundwater movement, resulting in separate groundwater sub-basins.
• Because each sub-basin has experienced different development patterns, and is significantly isolated from adjacent basins, groundwater in these sub-basins is being lost at different rates. The model depicts how each sub-basin has responded in the past and will respond into the future.
• The model indicates how quickly our groundwater is being depleted. Unfortunately, in many areas groundwater is not replenished by recharge, and even in areas where a very small amount of recharge does occur, it is not sufficient to maintain the current rates of groundwater use.
Summarizing the report, hydrogeologist Lindsey said, “The initial results consistently indicate that throughout the GWMA, demand for water from wells is met principally by storage depletion – and that because natural recharge has failed to keep pace with demand, groundwater resources continue to decline.”
Lindsey went on to explain that “Calculations of the ‘recoverable groundwater storage’ that remains suggest that over 50% of the storage that was available when development commenced has been removed and is not being replenished – and that in some groundwater sub-regions the situation is critical, with less than 40% of the initial recoverable storage remaining. Given that beneficial use of all ‘recoverable storage’ is impractical, it is likely that at current production rates, groundwater in storage throughout the GWMA may be depleted within two to three decades, and sooner within some groundwater sub-regions.”
The report includes the results of groundwater budget calculations for the entire GWMA area, and for four groundwater sub-regions (Odessa, Moses Lake, Royal Slope and Connell), which were completed as part of the modeling project. Groundwater budget calculations for the remaining 12 groundwater sub-regions have not been completed, although GWMA leaders sought state funding this year with expectations that the remaining sub-region water budget calculations would be completed next year.
Estimated age of water in municipal wells
Only two of the 25 GWMA city wells contain a high percentage of young water.
General concepts
• Groundwater is the only source of potable water for nearly 100% of the municipal and private well owners in the four-county area of the GWMA.
• Most cities have reported declining water levels, consistent with production-base wells. Even wells where the presence of relatively younger water implies recharge, the amount of recharge is not enough to sustain increasing population levels.
Data acquisition/evaluation
• In an effort to characterize groundwater from all major cities within the GWMA, hydrologists have taken a systematic and comparative approach to assess groundwater age and static water levels.
• GWMA has sampled most major municipal wells within city limits for geochemistry. By using a radiometric and multiple tracer approach and scientifically peer-reviewed models, we have undertaken the most comprehensive effort to date at producing a region-wide assessment of groundwater in cities.
• GWMA uses multiple lines of evidence to assess municipal water sources, including geochemistry, in-depth static water level analysis and personal interviews.
2011-2012 GWMA Groundwater Projects:
1. Construction of hydrologic assessment of each municipal water supply: GWMA will assess the future groundwater supplies for each of the 25 cities and towns inside the four-county area (Adams, Franklin, Grant and Lincoln Counties).
2. Identification of sustainable wells along east low canal: GWMA will assess wells along the east low canal to identify which farm wells may receive enough new water to be sustainable.
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