“The Colorado River: Lifeline of the Southwest” Online Slideshow
The Colorado River provides water to 25 million people in seven states and irrigation water to over 3 million acres of farmland. The online slideshow traces the river from its headwaters as it passes through the seven Basin states to the Gulf of Mexico. The slideshow conveys graphically the scale of the river and its tributaries, as well as its connections and expansive impact on the people who depend on it. Although the presentation includes over one hundred slides, the use of colorful graphics and limited text on each slide will keep viewers watching. Highlighted in the title, and emphasized throughout the slides, is the importance of the river and its resources to the longevity of the communities depending upon it. Whether learning about the Colorado River for the first time or revisiting familiar territory, viewers from a wide range of audiences will find the slideshow informative and engaging. Funding for the slideshow was provided by the Water for the West Foundation. This slideshow is free to view on Aquafornia and on the Foundation’s website under Free Programs and Information.
Streamflow Depletion by Wells-Understanding and Managing the Effects of Groundwater Pumping on Streamflow
Groundwater provides drinking water for millions of Americans and is the primary source of water to irrigate cropland in many of the nation’s most productive agricultural areas. Despite the many benefits of groundwater development, connected streams and rivers may suffer from reduced flows through a process called streamflow depletion by wells. This report, just released by the USGS, summarizes what is known about streamflow depletion, highlighting common misconceptions, and presenting new concepts to help water managers and others understand the effects of groundwater pumping on surface water.
Groundwater and surface-water systems are connected, and groundwater discharge is often a substantial component of the total flow of a stream. In many areas of the country, pumping wells capture groundwater that would otherwise discharge to connected streams, rivers, and other surface-water bodies. Groundwater pumping can also draw streamflow into connected aquifers where pumping rates are relatively large or where the locations of pumping are relatively close to a stream.
The report’s major conclusions throw into relief the water management issues related to balancing groundwater uses with preservation of streamflows. The report concludes that individual wells may have little effect on streamflow depletion, but small effects of many wells pumping within a basin can combine to produce substantial effects on streamflow and aquatic habitats. Basinwide groundwater development typically occurs over a period of several decades, and the resulting cumulative effects on streamflow depletion may not be fully realized for years. Streamflow depletion continues for some time after pumping stops because it takes time for a groundwater system to recover from the previous pumping stress. In some aquifers, maximum rates of streamflow depletion may occur long after pumping stops, and full recovery of the groundwater system may take decades to centuries. The major factors that affect the timing of streamflow depletion are the distance from the well to the stream and the properties and geologic structure of the aquifer. Streamflow depletion can affect water quality in the stream or in the aquifer. For example, in many areas, groundwater discharge cools stream temperatures in the summer and warms stream temperatures in the winter, providing a suitable year-round habitat for fish. Reductions in groundwater discharge to streams caused by pumping can degrade habitat by warming stream temperatures during the summer and cooling stream temperatures during the winter. Sustainable rates of groundwater pumping near streams depend on the total flow rates of the streams and the amount of reduced streamflow that a community or regulatory authority is willing to accept.
The report supports its conclusions with a wealth of technical explanation and examples in understandable prose and attractive explanatory graphics. Although not light reading, this report could be used as a reference for anyone with an interest in streams and rivers and the impacts on them of groundwater pumping.
The report, a product of the USGS Groundwater Resources Program, is available in print and at http://pubs.usgs.gov/ circ/1376/.
Ambient Groundwater Quality of Ranegras Plan Basin: A 2008-2011 Baseline Study- June 2012
The Arizona Department of Environmental Quality, as part of its Ambient Groundwater Monitoring Program, conducted a baseline groundwater quality study of the Ranegras Plain basin from 2008 and 2011, and has released two versions of the report in print and online: a 63-page report and a condensed 4-page fact sheet. Arizona Revised Statutes 49-225 mandates ongoing monitoring of waters of the state including its aquifers. The study is based on samples collected from 55 sites within the Ranegras Plain groundwater basin, which covers approximately 912 square miles in western Arizona within La Paz County.
According to the report, “Most groundwater pumped in the Ranegras Plain is used for irrigation in the central part of the basin.” As discussed in the report, the study determined that the most important factor affecting water quality in the Ranegras basin is the recharge age of the groundwater. Concerns with drinking water sources in the area involve recent recharge, which is generally preferred over older recharge. The study resulted in recommendations from ADEQ for private domestic well owners in the basin to have their drinking water tested for contaminants particularly arsenic, chromium, fluoride, and nitrate by a certified laboratory.