May 22, 2014

Mr. Leising

talked about all of the programs in which he was involved while working at the SNWA. Using maps and charts he talked about aquitards where water is prevented from entering the valley aquifer due to densely packed fill material. This scenario could be assumed for the Pahrump Basin. He described different aquifers in the Las Vegas Valley from which water is drawn. About 80% of recharge comes from the mountains surrounding the Las Vegas Valley which is confirmed by USGS isotopic studies. The Pahrump Valley primarily receives its recharge from the Spring Mountains. One study estimates that amount to be around 23,000 AF per year. The recharge rate could possibly be higher for the Pahrump Valley as the Las Vegas Valley had been underestimated for many years in the past.

Mr. Leising

discussed how water is taken from Lake Mead and injected into the Vegas Valley aquifer. Artificial recharge has helped to reverse the rate of depletion of the aquifer there. Recharge in the Pahrump aquifer may help alleviate declining water levels too. Ground subsidence and fissures occur as the water table drops due to compaction of soils. He described how poorer quality water may encroach into areas where levels are dropping. Water may be put back into the aquifer through the use of infiltration basins or using deep wells to inject water back into the ground. A good monitoring system is crucial to understand what is going on in the wells. Mr. Leising noted that the water levels have risen in the Las Vegas Valley by more than what had been expected considering the amount of water that has been artificially recharged. He feels that this indicates there is much more natural recharge occurring than has been estimated in many studies that have been done. This may also be the case in the 3 Groundwater Advisory Committee May 22, 2014 Pahrump Valley, but there is no way of knowing until a recharge program has been initiated. Permits are required from NDEP and the State Engineer to in order to perform artificial recharge due to the potential for contamination of the aquifer. He discussed some of those potential contaminants. A large distribution system will be required to move water around the basin. Geology is a major consideration in placement of an AR well. There must be complete understanding of hydrology and lithology of the aquifer before a program can be initiated. It is important to find a “sweet spot” in the valley where there is a high transmissivity rate that enables the most effective water recharge. He again stressed the importance of a good monitoring network such as the one conducted by the NWRPO for providing accurate data and a need for a water resource plan. Potential sources for water augmentation need to be identified. Mr. Leising noted that the Las Vegas Valley also has a very aggressive conservation plan in place. Finally, he emphasized the importance of the willingness to cooperate between the public and government agencies. Without that nothing can be accomplished. Committee members proceeded to ask questions of Mr. Leising. It was noted that water taken from Lake Mead is treated before it is injected into the aquifer. No treated effluent is reinjected. RIB’s will not work effectively in the Las Vegas Valley due to the tight geology. There are 78 permitted injection wells in the valley but they are not all used at the same time.

Mr. Leising

feels that an injection system would work in the Pahrump Valley but it is a matter finding a source, getting permits and having a distribution system built. The injection of water into the aquifer will not affect one’s right to withdraw water from the aquifer. A lot of good data is needed in order to find out if Basin 162 is in a state of “balance” to determine what type of action needs to be taken. Mr. Leising noted that there is much more water lost proportionally through evapotranspiration from irrigation of grass and alfalfa than there is for a lake. He did not know if perennial yield could be increased through recharge. Levi Kryder related that stratigraphic and borehole geophysical data has been gathered for wells drilled in the Pahrump Valley by the NWRPO during their water studies. However, collection of borehole geophysical data is not required when drilling a domestic well, so there are relatively few other wells where this data was collected.

Mr. Leising

related that he may be able to help with providing data that could be used to determine what the perennial yield for the Pahrump Valley might be. He related that RIB’s are a cheaper alternative to injection wells but it is all dependent upon the geology of the area. RIBS can utilize treated effluent whereas injection wells cannot due to potential for contamination of the aquifer.

Mr. Kryder

went on to show where groundwater levels were increasing and decreasing through the use of a water table elevation change created from water level data collected in the Water Level Measurement Program that has been taken over by the Nye County Water District from the NWRPO. These data show that water levels are increasing on the fan while areas on the valley floor are experiencing different rates of depletion or remaining fairly stable. Depletion can be correlated directly with the density of domestic wells in a particular area. This particular map covers a 9 year period of data gathering. It is very apparent that water from the fan is unable to readily permeate into the valley floor aquifer. This map shows the poor transmissivity of the soils in the valley floor, much like what occurs in the Las Vegas Valley. Geophysical logging and injection testing of potential sites are necessary to determine whether an ASR project may be feasible for the Pahrump Valley. A member of the audience related how her well levels were dropping at an annual rate of approximately 1.5 feet per year. This well is located in an area of high well density. Joe Leising noted that the hydrologic response time for water to enter the valley aquifer was around 7 years in the Las Vegas Valley and is probably similar for the Pahrump Valley.

Mr. Leising

talked about how climate effects water flow patterns to the aquifer. Mr. Kryder explained that there are many sinkholes and fissures throughout the Pahrump Valley as well. Tim Hafen noted that water levels were rising on the fan due to the fact that water is no longer pumped for agricultural operations. Gregory Hafen hoped that the water metering program can continue on as a valuable source of important data. 5 Groundwater Advisory Committee May 22, 2014

Mr. Kuver

noted that no matter how water is distributed throughout the valley, eventually we are going to run out if measures are not taken to curb usage.

Mr. Lacy

related that all ideas must be presented before an evaluation of each can be completed. Outside studies may be necessary to complete a thorough analysis of some proposals. Wendy Barnett related that, at times, this issue can become very emotional. It is necessary that all ideas be submitted to the Water District ASAP so they can be included in the back-up for the Workshop. Ideas may also be submitted anonymously. Tim Hafen noted that since the majority of agricultural irrigation has ceased in the valley, water levels have been increasing in the wells on the fan. He also related that residential growth does pay for itself in the form of tax revenue to the county and discussed Mr. Kuver’s desire to call for proof of beneficial use on lots that have already had water rights relinquished for future use. There was no further comment.