Tulare Lake

The tradeoff between water savings and salinization prevention in dryland irrigation

Advances in Water Resources (Elsevier) | December 7th, 2023

Soil salinization is a global phenomenon that affects large tracts of arid farmland worldwide. It contributes to the loss of soil fertility, declining yields, and – in

Soil salinization is a global phenomenon that affects large tracts of arid farmland worldwide. It contributes to the loss of soil fertility, declining yields, and – in the most severe cases – land unsuitability for cultivation. Irrigation water applications are both the main cause of and the solution to, anthropogenic (or ‘secondary’) salinization because salt typically enters the soil column as dissolved in irrigation water and leaves it through excess water applications (e.g., leaching). Excess leaching, which places additional water costs in areas affected by water scarcity, can be achieved with different irrigation techniques and practices. Here, by complementing a process-based crop water model with a salt balance of the shallow soil, we investigate the tradeoff between root zone salinization and water conservation to limit withdrawals from the water source. We evaluate how such a tradeoff is achieved under different irrigation technology and excess leaching practices. Considering as a case study the cultivation of tomatoes in Egypt, we find that drip and furrow irrigation allows for better control of salt accumulation, thus preventing crop exposure to salt stress. Drip irrigation achieves this goal with minimal water applications because it maintains the soil wetter. Thus, the (rare) rainfall events find more suitable conditions to drain the excess moisture. Conversely, by using more irrigation water (and ‘less efficiently’), furrow irrigation allows for higher rates of soil drainage and salt leaching. The irrigation schedule typically adopted with sprinkler irrigation allows for soil drying, thus limiting the ability of rainfall events to drain the soil and leach its salts. Collectively, these results highlight the key role of irrigation technology and practices in the management of secondary salinity in dryland agriculture. Specifically, there is a tradeoff between minimizing water use and preventing salt accumulation in the root zone. Drip irrigation exhibits the co-benefit of achieving both goals, while furrow irrigation limits soil salinity at the cost of requiring greater volumes of applied irrigation water.

The Untapped Potential of California’s Urban Water Supply: Water Efficiency, Water Reuse, and Stormwater Capture

Pacific Institute | April 12th, 2022

In this assessment, we quantify the potential for a range of water strategies in urbanized parts of California to both reduce inefficient and wasteful water uses and expa

In this assessment, we quantify the potential for a range of water strategies in urbanized parts of California to both reduce inefficient and wasteful water uses and expand local water supplies. This assessment finds that urban water-use efficiency improvements could reduce statewide urban water use by 2.0 million to 3.1 million acre-feet per year (AFY). The reuse potential of municipal wastewater is 1.8 million to 2.1 million AFY, and the stormwater capture potential is 580,000 AFY in a dry year to as much as 3.0 million AFY in a wet year. Previous assessments have shown that these efficiency and supply options are more cost effective than traditional – and increasingly hard to implement – options to expand supply. Programs to tap this potential would tremendously help solve California’s long-standing water problems.

The Water Districts of California

Association of California Water Agencies (ACWA) | April 1st, 1979

The West Wide Drought Tracker: Drought Monitoring at Fine Spatial Scales

American Meteorological Society (AMS) | September 1st, 2017

 The western United States has seen increases in population and water use over the past century. Total water use has remained relatively unchanged over the past several

 The western United States has seen increases in population and water use over the past century. Total water use has remained relatively unchanged over the past several decades due to water conservation efforts. However, water scarcity has become more acute across much of this semiarid region during recent decades due to long-term declines in water storage juxtaposed with the region’s notable hydroclimatic variability. Observed declines in mountain snowpack and increases in atmospheric demands tied to long-term warming trends have further exacerbated water scarcity and increased the importance of monitoring efforts given the array of social, economic, and ecosystem sectors dependent upon the already stressed water supply. The recent severe drought in California and protracted drought across much of the southwestern United States over the past couple decades have prompted demand for accessible drought decision-making information at appropriate spatial scales across the western United States. 

Thousands of domestic and public supply wells face failure despite groundwater sustainability reform in California’s Central Valley

Nature Portfolio (Springer Nature) | September 8th, 2023

Time Limits for Western Water Rights

Natural Resources and Environment (SSRN) | November 1st, 2022

Time-varying land subsidence detected by radar altimetry: California, Taiwan and north China

Nature Portfolio (Springer Nature) | June 21st, 2016

Contemporary applications of radar altimetry include sea-level rise, ocean circulation, marine gravity, and icesheet elevation change. Unlike InSAR and GNSS, which are wi

Contemporary applications of radar altimetry include sea-level rise, ocean circulation, marine gravity, and icesheet elevation change. Unlike InSAR and GNSS, which are widely used to map surface deformation, altimetry is neither reliant on highly temporally-correlated ground features nor as limited by the available spatial coverage, and can provide long-term temporal subsidence monitoring capability. Here we use multi-mission radar altimetry with an approximately 23 year data-span to quantify land subsidence in cropland areas. Subsidence rates from TOPEX/POSEIDON, JASON-1, ENVISAT, and JASON-2 during 1992–2015 show time-varying trends with respect to displacement over time in California’s San Joaquin Valley and central Taiwan, possibly related to changes in land use, climatic conditions (drought) and regulatory measures affecting groundwater use. Near Hanford, California, subsidence rates reach 18 cm yr with a cumulative subsidence of 206 cm, which potentially could adversely affect operations of the planned California High-Speed Rail. The maximum subsidence rate in central Taiwan is 8 cm yr. Radar altimetry also reveals time-varying subsidence in the North China Plain consistent with the declines of groundwater storage and existing water infrastructure detected by the Gravity Recovery and Climate Experiment (GRACE) satellites, with rates reaching 20 cm yr and cumulative subsidence as much as 155 cm.

To Stop Desert Encroachment

Scientific American | November 1st, 1938

When Spanish vaqueros first entered the interior valley of California they saw only a vast expanse of desert, broken infrequently by patches of green vegetation a

When Spanish vaqueros first entered the interior valley of California they saw only a vast expanse of desert, broken infrequently by patches of green vegetation along the water courses. Little did they dream that in a span of two generations the region would become one of the world's garden spots, the home of thousands of prosperous families, and the source of millions of tons of food products known around the world. They did not envision the romance and adventure that marked the development of this great inland empire-now a two billion dollar agricultural wonderland built by irrigation and wholly dependent upon a single natural resource-water.

Total Water Management Study for the Central Valley Basin, California, Central Valley Project Intermittent Surface Water Supply, Working Document No. 6

U.S. Bureau of Reclamation (USBR) | April 1st, 1975

Total Water Management Study for the Central Valley Basin, California, Central Valley Project Water Yield Risk Working Document No. 5

U.S. Bureau of Reclamation (USBR) | February 1st, 1975