Past and Present Water Supplies

Since the beginning of the 20th century, El Paso County has relied on both surface water and groundwater for municipal water supply. Currently, El Paso Water Utilities (EPWU) supplies about 90% of all municipal water in El Paso County. Surface water is supplied from the Rio Grande. The Rio Grande flows that are diverted in the El Paso area are primarily derived from snowmelt runoff in southern Colorado and northern New Mexico. Historically, there are also occasional flood surges associated with storm systems in the summer monsoon season. Spring runoff is stored in Elephant Butte Reservoir in southern New Mexico before releases are made for irrigation and municipal use in southern New Mexico and the El Paso area. EPWU is a customer of the local irrigation district (El Paso County Water Improvement District No.1), and obtains water through ownership of water rights land and leasing of water rights from agricultural water rights holders in El Paso County.

Groundwater supplies are pumped from the Mesilla Bolson and the Hueco Bolson and are shown in the figure below. These groundwater basins underlie portions of New Mexico, Texas and Chihuahua. Groundwater occurs in unconsolidated fluvial, alluvial, and lacustrine sediments. The Rio Grande plays an important role in the recharge and discharge of both groundwater basins.


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EPWU pumping in the Hueco Bolson peaked at about 80,000 acre-feet per year (AF/yr) in 1989. As a result of concerns regarding the long-term ability to continue this level of pumping (e.g. Muller and Price, 1979 and Boyle Engineering, 1991), EPWU implemented the following water management strategies: 1) adopted a rate structure that increases the cost of water for high use, 2) promoted water conservation through various incentive programs, 3) increased the use of Rio Grande Water, and 4) expanded the reuse of reclaimed water.

As shown below, EPWU pumping in the Hueco Bolson in 2002 was below 40,000 AF/yr for the first time since 1967. Hueco pumping increased in 2003 and 2004 from 2002 levels due to a drought and the associated reduction in surface water diversions. Pumping again dropped below 40,000 AF/yr in 2005 as a result of a return of nearly full river allocation conditions. The conjunctive use of surface water and groundwater (increasing groundwater pumping in times of surface water shortages) to meet overall demands is part of EPWU's overall water supply strategy.

Water Production Chart
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The surface water plants have a combined capacity of 100 mgd. Under normal river flow conditions, the plants operate seven months during the year (i.e. during the irrigation season). EPWU is a customer of El Paso County Water Improvement District No.1, and receives water from the Rio Grande Project via its ownership of lands within the project area or through leases from water rights holders. Currently, El Paso has water rights of about 70,000 AF/yr from the Rio Grande Project (FWTRPG, 2011).

As shown below, total demand has been declining since the late 1990s due to conservation and pricing strategies. Current total demand is about 118,000 AF/yr. Per capita demand has been reduced from about 225 gallons per person per day in the 1970s to about 133 gallons per person per day in 2010.

Total Water Production
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Water Planning in Texas

In 1991, El Paso Water Utilities completed its own 50 year Water Resource Management Plan (1991-2040). This plan recognized the importance of water conservation and the increased use of surface water to meet future demands. The current process of water planning was enacted by the 75th Texas State Legislature. Senate Bill 1 emphasizes state water planning at a localized level rather than a centralized state level. The legislation divides the state into 16 regions each with the task of producing a 50-year regional water plan every five years. The 2011 Water Plan represented the third cycle of regional water planning. Previous water plans were completed in 2001 and in 2006. El Paso is located in the Far West Texas Region (Region E) along with 6 other counties in far west Texas. The entire 2011 Far West Texas (Region E) Water Plan can be viewed at http://www.twdb.state.tx.us/wrpi/rwp/3rdRound/2011_RWP/RegionE.

Summary of Far West Texas Water Plan (Region E) for El Paso Water Utilities

The Far West Texas Water Plan follows a process that is mandated by the Texas Legislature. All regional water plans are approved by the Texas Water Development Board. These plans provide an evaluation of current and future populations, populations, demands, supply sources, water management strategies and costs. Projects that are proposed for funding through TWDB must be included in the State Water Plan. As presented in the 2011 regional water plan is a summary of the El Paso County population served by El Paso Water Utilities. See table below.

Project of El Paso County Population Served
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Based on current capacities of wells and surface water plants, and the limitation that surface water is only available during the irrigation season, total available municipal supply in El Paso Water Utilities is about 131,000 AF/yr. This total includes about 6,000 AF/yr of reclaimed water supply that is available independent of drought conditions. Under full surface water allocation conditions, municipal surface water supply is about 60,000 AF/yr. Under these conditions, Hueco Bolson groundwater pumping supply is about 40,000 AF/yr, and Mesilla Bolson pumping supply is about 25,000 AF/yr. Under drought-of-record conditions, it is expected that surface water supplies would drop to 10,000 AF/yr. During drought-of-record conditions, pumping supplies in the Hueco Bolson increase to 80,000 AF/yr, Mesilla Bolson pumping supplies increase to 35,000 AF/yr, reclaimed water supply would remain at 6,000 AF/yr for a full municipal supply of 131, 000 AF/yr.

El Paso Water Utilities conjunctively uses surface water and groundwater to meet demands. Under a full river allocation, use of surface water will be maximized and the pumpage from the Hueco Bolson will be minimized. Conversely, during times of drought with a low river allocation, pumpage from the Hueco Bolson will be maximized. During a drought, pumping from the Mesilla Bolson would increase slightly. The figure below summarizes these conjunctive use scenarios. Scenario 1 represents a full surface water allocation scenario. Scenario 6 represents a drought-of-record scenario. Scenarios 2 through 5 represent intermediate surface water allocation scenarios that are less than full allocation, but more than drought-of-record conditions.


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The conjunctive use management of surface water and groundwater resources recognizes that there are limits to surface water supplies and limits to groundwater supplies. The most significant limitation to the surface water supply is that droughts occur, and surface water allocations are reduced in some years. As a result of reduced river availability, groundwater pumping is increased in order to meet demands. The management of local groundwater requires the recognition of limits with respect to the ability of local groundwater basins to supply water reliably over many decades. Simply increasing local groundwater pumping to meet increased demands has been shown to be an ineffective groundwater management strategy in El Paso Water Utilities in terms of water quantity (declining groundwater levels) and water quality (brackish groundwater intrusion).

The 2011 regional plan includes supplies that are currently available to El Paso Water Utilities. These supplies include current conjunctive use of groundwater and surface water and reclaimed water. The current supply available to El Paso Water Utilities is 131,000 acre-feet per year. When future demands exceed existing supplies, water management strategies are developed. In the 2011 plan, El Paso Water Utilities has included additional water management strategies by the year 2020 to meet future demands. A listing and brief description of the water management strategies included in the 2011 Region E Water are presented below.

Conservation
Reduction of municipal water consumption may be achieved with the implementation of conservation programs that reduce per capita usage and prevent water waste. Components of the EPWU Water Conservation Program include, rate structure which penalize high consumption, residential water restrictions, rebate programs for the replacement of inefficient water fixtures, introduction of native landscaping to reduce irrigation requirements, public education and enforcement. EPWU has been implementing an aggressive water conservation program for the past 20 years. Continued water conservation is an important component of the 50 year water plan.

Reclaimed Water Supply
A portion of wastewater effluent collected from the Northwest, Haskell, Bustamante, and Fred Hervey plants is currently being redirected into a water distribution system (purple pipe distribution) for users of reclaimed water. Reclaimed water serves the demand of golf courses, parks, schools, industry and cooling water for electric power plants. Current reuse projects provide 6,000 acre-feet per year for EPWU. Reuse supply in the year 2060 is estimated to reach 12,000 AF/year.

New Conjunctive use supplies (Rio Grande and groundwater)
Additional surface water treatment capacity and production wells will be needed. Additional use of surface water is subject to approval of the El Paso County Water Improvement District No. 1 and the Bureau of Reclamation. An additional 5,000 AF/year of conjunctive use supplies are needed by 2020.

Recharge of groundwater with treated surface water (NEW)
This is a new water management strategy in the Region E Water Plan. Early in the irrigation season, when the demand is low, treated surface water from the Rio Grande is available to recharge groundwater of the Hueco Bolson. Up to 5,000 AF/year of additional water per year is available recharge the Hueco Bolson through spreading basins constructed in Northeast El Paso. This water management strategy is scheduled to be implemented by year 2020, or sooner.

Desalination of Irrigation Return Flows (NEW)
This is a new water management strategy in the Region E Water Plan. Irrigation return flow is of lower quality than water during irrigation season. The concept behind this strategy is to treat 5 million gallons per day (MGD) with Reverse Osmosis membranes and blend with an additional 5 MGD of return flow to produce 10 MGD of water. This strategy is scheduled to be implemented in the year 2020 and would produce 2,700 AF/year.

Groundwater from Capitan Reef
This is water importation project from property purchased by the EPWU. Wells and pipelines are to be constructed. Water quality does not require treatment prior to use. Importation is proposed to begin in 2040 (if needed). Location map is shown below.

Groundwater from Dell City Area.
Groundwater importation project from the Dell City area. Additional properties would need to be purchased. Wells and pipelines would be constructed. This water quality would require treatment before use. This would accomplished through either blending or desalination. Importation of 10,000 AF/year is proposed to begin in 2050 (if needed). Location map is shown below.


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The timing of implementation of each water management strategy and their quantity is presented in the table below. The additional water from various water management strategies are added to the current supply of 131, 000 AF/year to make up the total proposed supply for El Paso Water Utilities. The amount of total proposed supply is compared to the demand for El Paso Water Utilities for each decade (2010-2060). The amount of water shown in surplus supplies is the difference between total proposed supply and the demand for any given decade shown in the table below.


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Discussion

EPWU current available supply of water is 131,000 AF/yr. Additional water management strategies (water supplies) are needed by the year 2020 to meet increased demands. The strategies to be used include conservation, reclaimed water supply, new conjunctive use supplies (Rio Grande and groundwater), recharge of groundwater with treated surface water, and desalination of irrigation return flows.

Groundwater importation begins in the year 2040 from Capitan Reef in the amount of 10,000 AF/year. The amount of water needed from the Capitan Reef properties would remain at 10,000 AF/year through the balance of the planning period. The best available information regarding the hydrogeology is from Reed (1965 and 1973). Reed (1965) estimated that recharge to the Diablo Farms area is about 15,400 AF/yr. Reed (1973) estimated that annual pumping in the range of 25,000 to 30,000 AF/yr would result in annual groundwater level declines of about 2 to 3.5 feet. The relatively low amount of projected pumping contained in the plan acknowledges the uncertainty in how much can be pumped in a sustainable manner, and recognizes the potential for brackish groundwater intrusion.

Importation of groundwater from the Dell City area would begin in 2050 with 10,000 AF/yr. In 2060, the amount of importation would increase to 20,000 AF/year. Groundwater from the Dell City is brackish and would require some form of treatment prior to use. This would be accomplished through either desalination and/or blending. El Paso Water Utilities would need to purchase additional water rights properties prior to importation.

Due to successful water management implementation, groundwater importation has been delayed until 2040. This is 10 years later than in the previous plan. The total amount of groundwater importation is 30,000 AF/year in 2060. This is 50% less than the importation amount included in the 2006.

Participation in the regional planning process is an important factor in the water resources management for El Paso. The participatory nature of regional water plan development is an ideal forum to work with others in the region to manage water on a regional basis. The fourth cycle of Regional Water Planning will begin in 2012 with the evaluation of population data from the 2010 Census. The next Regional Water Plan will be completed in 2016.