Groundwater depletion and sustainability of irrigation in the US High Plains and Central Valley

National Academy of Sciences (NAS) | June 12th, 2012

Aquifer overexploitation could significantly impact crop production in the United States because 60% of irrigation relies on groundwater. Groundwater depletion in

Aquifer overexploitation could significantly impact crop production in the United States because 60% of irrigation relies on groundwater. Groundwater depletion in the irrigated High Plains and California Central Valley accounts for ∼50% of groundwater depletion in the United States since 1900. A newly developed High Plains recharge map shows that high recharge in the northern High Plains results in sustainable pumpage, whereas lower recharge in the central and southern High Plains has resulted in focused depletion of 330 km3 of fossil groundwater, mostly recharged during the past 13,000 y. Depletion is highly localized with about a third of depletion occurring in 4% of the High Plains land area. Extrapolation of the current depletion rate suggests that 35% of the southern High Plains will be unable to support irrigation within the next 30y. Reducing irrigation withdrawals could extend the lifespan of the aquifer but would not result in sustainable management of this fossil groundwater. The Central Valley is a more dynamic, engineered system, with north/south diversions of surface water since the 1950s contributing to ∼7×higher recharge. However, these diversions are regulated because of impacts on endangered species. A newly developed Central Valley Hydrologic Model shows that groundwater depletion since the 1960s, totaling 80 km3, occurs mostly in the south (Tulare Basin) and primarily during droughts. Increasing water storage through artificial recharge of excess surface water in aquifers by up to 3 km3 shows promise for coping with droughts and improv ing sustainability of groundwater resources in the Central Valley.

How much potable water is saved by wastewater recycling? Quasi-experimental evidence from California

Resources, Conservation & Recycling (Elsevier) | October 6th, 2021

Recently, California has made large investments in wastewater recycling to replace applications that use potable water. It may be expected that the use of recycled water

Recently, California has made large investments in wastewater recycling to replace applications that use potable water. It may be expected that the use of recycled water reduces potable water use, but such an equivalency is not assured. The addition of recycled water infrastructure in a large Californian water district creates a natural experiment where this work tests how recycled water usage affects primary potable water. This is done using econometric methods for causal inference in an observational setting that mirror a randomized control trial (RCT). From 2001 to 2014, a number of public parks were given recycled water infrastructure, while others in those regions remained exclusively on potable supply. A two-way fixed effects regression is used to produce a difference-in-differences estimate of the average treatment effect of recycled water on total and potable water usage. The results indicate that potable water usage is reduced significantly when a park is connected to the recycled water supply. The estimated rate of displacement in the study period is 81.7%, meaning each unit of recycled water use avoided 0.817 units of potable water usage, which implies the connection of parks to recycled water supply increases total water use. The analysis provides, to the best of our knowledge, the first empirical estimate of the water savings claimed by urban water recycling programs, and the first empirical estimate of displacement using quasi-experimental methods. The methodology can be utilized to evaluate the effectiveness of recycling programs around the world.

Irrigated Agriculture Technologies, Practices, and Implications for Water Scarcity

U.S. Government Accountability Office (GAO) | November 12th, 2019

Demand for freshwater surpasses the amount naturally available in some areas of the United States. The agriculture sector competes for this limited resource, and withdraw

Demand for freshwater surpasses the amount naturally available in some areas of the United States. The agriculture sector competes for this limited resource, and withdraws and consumes the most freshwater of any user in the nation. GAO was asked to conduct a technology assessment around agricultural water use. This report provides an overview of irrigation technologies and on-farm water conservation practices, factors influencing the adoption of these technologies, and implications of their use for water scarcity. In conducting this assessment, GAO reviewed scientific literature; convened an expert meeting with the assistance of the National Academies; visited farmers, academics, and industry representatives; interviewed officials from federal agencies; modeled water use in an illustrative watershed; and performed a regression analysis on U.S. Department of Agriculture irrigation, crop, and technology data. GAO describes two policy options that federal policymakers could consider relating to irrigation technology and discusses their benefits and challenges.

Irrigating Machinery on the Pacific Coast

Scientific American | December 17th, 1887

In offering the present paper to the Institution of Mechanical Engineers, the author does so with a tolerably complete knowledge of the very advanced practice in England

In offering the present paper to the Institution of Mechanical Engineers, the author does so with a tolerably complete knowledge of the very advanced practice in England in this class of machinery: and his purpose is mainly to explain the differences that have been called for by local circumstances in California. Character of the Country: The western or Pacific slope of the Sierra Nevada or coast range of mountains in California is very abrupt, the crests of the range being so near that the snow is visible from the coast during the whole year. Hundreds of streams cross this narrow country, falling either direct into the Pacific Ocean or into the great basin formed by the Sacramento and San Joaquin rivers. These two rivers. the largest in California, run in opposite directions nearly parallel with the coast and meet at the Bay of San Francisco forming ac ontinuous valley 400 miles long and from 50 to 100 miles wide. The small streams for the most part are fed by melting snow in the summer; and every gulch or canon has its rivulet or brook. They increase in volume until they pass into or through the hills at the foot of the mountain range; and there, unless of considerable size, they may wholly disappear in summer by percolation through the silt or by evaporation. Streams exposed to the torrid air which in summer sweeps across the sand deserts of Southern California are dried up with wonderful rapidity. The evaporation from Salt Lake, exposed to the same dry wind, is sometimes equal to half an inch per day. or 64 million tons of water. Not withstanding this great loss by evaporation, the quantity of water falling into the ocean on the coast of California has been estimated at 100 million cubic feet or 2 3/4 million tons per minute, enough, if distributed properly, to irrigate 25,000 square miles.

Irrigation

Scientific American | January 10th, 1903

Irrigation has been practised in America from time immemorial by the town-building Pueblo Indian tribes inhabiting portions of New Mexico and Arizona. Their ancie

Irrigation has been practised in America from time immemorial by the town-building Pueblo Indian tribes inhabiting portions of New Mexico and Arizona. Their ancient canals may still be traced across the broad valleys. through which are scattered the almost innu merable ruins of community dwellings. On the mesas of southwestern Colorado and adjacent portions of Utah, Arizona, and New Mexico are found the wonderful cliff dwellings, and in the little valleys near these may be seen ditches which were in use perhaps a thousand or more years ago.

Irrigation

Scientific American | January 17th, 1903

Irrigation in California

Scientific American | January 5th, 1884

Irrigation in California

Scientific American | January 4th, 1890

Irrigation in Southern California

Scientific American | December 17th, 1904

As an example of the beneficent results of irrigation of desert lands, a project which has been undertaken in Southern California is probably one of the most notable i

As an example of the beneficent results of irrigation of desert lands, a project which has been undertaken in Southern California is probably one of the most notable in America, for its promoters selected a region most of which was entirely devoid of vegetation in any form, the soil, if it can be called such, not even containing enough elements of fertility to nourish the sparse vegetation found in the so-called desert of the Southwest. Prior to the reclamation of this land, one could travel for miles without seeing any vegetation. Most of the area referred to forms a part of the Colorado Valley, and is situated in San Diego County. The head of the canal was located on the river at a point seven miles west of Yuma, Arizona, and but a short distance from the boundary between California and Mexico. Here the elevation is 120 feet above sea level, a sufficient altitude to give an average fall of from four to six feet to the mile. It was found impossible to construct the waterway in a straight line, owing to the topography of the country, and in its course it makes a wide detour, passing through a portion of the Mexican republic. It is unique from the fact that it is probably the only international irrigation canal in the world, the water being used to cultivate a considerable area in the southern republic.

Irrigation in the Earth system

Nature Portfolio (Springer Nature) | June 20th, 2023