Investigating Factors Contributing to Phytoplankton Biomass Declines in the Lower Sacramento River

University of California, Davis (UC Davis) | March 23rd, 2023

Investigating Runoff Efficiency in Upper Colorado River Streamflow Over Past Centuries

American Geophysical Union (AGU) | January 5th, 2018

With increasing concerns about the impact of warming temperatures on water resources, more attention is being paid to the relationship between runoff and precipitat

With increasing concerns about the impact of warming temperatures on water resources, more attention is being paid to the relationship between runoff and precipitation, or runoff efficiency. Temperature is a key influence on Colorado River runoff efficiency, and warming temperatures are projected to reduce runoff efficiency. Here, we investigate the nature of runoff efficiency in the upper Colorado River (UCRB) basin over the past 400 years, with a specific focus on major droughts and pluvials, and to contextualize the instrumental period. We first verify the feasibility of reconstructing runoff efficiency from tree‐ring data. The reconstruction is then used to evaluate variability in runoff efficiency over periods of high and low flow, and its correspondence to a reconstruction of late runoff season UCRB temperature variability. Results indicate that runoff efficiency has played a consistent role in modulating the relationship between precipitation and streamflow over past centuries, and that temperature has likely been the key control. While negative runoff efficiency is most common during dry periods, and positive runoff efficiency during wet years, there are some instances of positive runoff efficiency moderating the impact of precipitation deficits on streamflow. Compared to past centuries, the 20th century has experienced twice as many high flow years with negative runoff efficiency, likely due to warm temperatures. These results suggest warming temperatures will continue to reduce runoff efficiency in wet or dry years, and that future flows will be less than anticipated from precipitation due to warming temperatures.

Investigating the Link Between Surface Water and Groundwater in the Tule Lake Subbasin, Oregon and California

Portland State University | August 13th, 2014

Water allocation in the upper Klamath Basin of Oregon and California has been challenging. Irrigators have increasingly turned to groundwater to make up for surf

Water allocation in the upper Klamath Basin of Oregon and California has been challenging. Irrigators have increasingly turned to groundwater to make up for surface water shortages because of shifts in allocation toward in-stream flows for Endangered Species Act-listed fishes. The largest increase in groundwater pumping has been in and around the Bureau of Reclamation’s Klamath Irrigation Project, which includes the Tule Lake subbasin in the southern part of the upper Klamath Basin. Previous groundwater flow model simulations indicate that water level declines from pumping may result in decreased flow to agricultural drains in the Tule Lake subbasin. Agricultural drains on the Klamath Project are an important source of water for downstream irrigators and for the Tule Lake and Lower Klamath Lake National Wildlife Refuges. To better assess the impact of increased pumping on drain flow and on the water balance of the groundwater system, flow data from agricultural drains were evaluated to investigate the changes that have taken place in groundwater discharge to drains since pumping volumes increased. Additionally, a fine-grid groundwater model of the Tule Lake subbasin was developed based on the existing regional flow model. The fine-grid model has sufficient vertical and horizontal resolution to simulate vertical head gradients, takes advantage of time-series data from 38 observation wells for model calibration, and allows agricultural drains to be more explicitly represented. Results of the drain flow analysis show that the groundwater discharge to agricultural drains has decreased by approximately 4000 hectare-meters from the 1997-2000 average discharge. Most of this decrease takes place in the northern and southeastern portions of the subbasin.  Results of the groundwater model show that the initial source of water to wells is groundwater storage. By 2006, approximately 56% of the water from wells is sourced from agricultural drains.

Investigating the Role of Snow Water Equivalent on Streamflow Predictability during Drought

American Meteorological Society (AMS) | October 20th, 2022

Snowpack provides the majority of predictive information for water supply forecasts (WSFs) in snow-dominated basins across the western United States. Drought conditions t

Snowpack provides the majority of predictive information for water supply forecasts (WSFs) in snow-dominated basins across the western United States. Drought conditions typically accompany decreased snowpack and lowered runoff efficiency, negatively impacting WSFs. Here, we investigate the relationship between snow water equivalent (SWE) and April–July streamflow volume (AMJJ-V) during drought in small headwater catchments, using observations from 31 USGS streamflow gauges and 54 SNOTEL stations. A linear regression approach is used to evaluate forecast skill under different historical climatologies used for model fitting, as well as with different forecast dates. Experiments are constructed in which extreme hydrological drought years are withheld from model training, that is, years with AMJJ-V below the 15th percentile. Subsets of the remaining years are used for model fitting to understand how the climatology of different training subsets impacts forecasts of extreme drought years. We generally report overprediction in drought years. However, training the forecast model on drier years, that is, below-median years (P15, P57.5], minimizes residuals by an average of 10%in drought year forecasts, relative to a baseline case, with the highest median skill obtained in mid- to late April for colder regions. We report similar findings using a modified National Resources Conservation Service (NRCS) procedure in nine large Upper Colorado River basin (UCRB) basins, highlighting the importance of the snowpack–streamflow relationship in streamflow predictability. We propose an “adaptive sampling” approach of dynamically selecting training years based on antecedent SWE conditions, showing error reductions of up to 20% in historical drought years relative to the period of record. These alternate training protocols provide opportunities for addressing the challenges of future drought risk to water supply planning.

Investigation on the Feasibility of Developing Uniform Water Recycling Criteria for Direct Potable Reuse

California State Water Resources Control Board (SWRCB) | December 29th, 2016

In 2010, the California Legislature enacted Senate Bill (SB) 918 (Chapter 700, Statutes of 2010), which added sections 13560-13569 (Division 7, Chapter 7.3) to the Water

In 2010, the California Legislature enacted Senate Bill (SB) 918 (Chapter 700, Statutes of 2010), which added sections 13560-13569 (Division 7, Chapter 7.3) to the Water Code regarding potable reuse of recycled water. SB 918 defined the term “direct potable reuse”1 and directed the California Department of Public Health (CDPH) to investigate the feasibility of developing uniform water recycling criteria for direct potable reuse (DPR), convene an expert panel to study the technical and scientific issues, and provide a final report to the Legislature by December 31, 2016. The main difference between DPR and indirect potable reuse (IPR) is DPR’s lack of a meaningful environmental buffer. In 2013, the Legislature enacted SB 322 (Chapter 637, Statutes of 2013), which amended Chapter 7.3 of the Water Code to require that an advisory group subject to the Bagley-Keene Open Meeting Act be convened to advise the expert panel and the State Water Board in the development of the feasibility report. SB 322 additionally tasked the expert panel to assess whether additional areas of research are needed to be able to establish uniform regulatory criteria for DPR and to recommend an approach for accomplishing any additional needed research in a timely manner. SB322 required that a draft report summarizing the expert panel research recommendations be prepared by June 30, 2016, and a draft feasibility report be provided to the public for comment by September 1, 2016.

Investigation on the Feasibility of Developing Uniformwater Recycling Criteria ror Direct Potable Reuse

California State Water Resources Control Board (SWRCB) | December 1st, 2016

The population of California is projected to increase from 38 million to 50 million by the year 2049. This population increase will have a dramatic impact on the water ne

The population of California is projected to increase from 38 million to 50 million by the year 2049. This population increase will have a dramatic impact on the water needs of the State. To address this increased water need, the State will take a variety of actions as outlined in the Governor’s California Water Action Plan, first released in 2014 and recently updated in 2016 (CA Natural Resources Agency, 2016). One component of that plan is to increase the use of recycled water. The State Water Board has set a mandate of increasing the use of recycled water by 200,000 acre-foot per year (AFY) by 2020 and an additional 300,000 AFY by 2030. Although the use of recycled water for non-potable uses such as agricultural and landscape irrigation is already well established and has been regulated for decades in California, increasing the use of recycled water for both non-potable uses as well as a source of potable water (“potable reuse”) is important for the State to be able to meet this mandate. For example, groundwater replenishment (groundwater recharge), which is an indirect form of potable reuse, has the capacity to reuse 200,000 acre-feet of recycled water a year via just eight projects throughout California. Accordingly, the State Water Board revised and adopted uniform water recycling criteria for groundwater replenishment in 2014 and is in the process of establishing uniform water recycling criteria for the augmentation of surface water reservoirs used as a source of drinking water supply, which is another form of indirect potable reuse.

Investing In Clean Agriculture: How California Can Strengthen Agriculture, Reduce Pollution And Save Money

Pacific Institute | February 8th, 2005

Global competition, suburban encroachment, tighter regulations, and rising input costs are making farming in California more difficult and, in some cases, less profitable

Global competition, suburban encroachment, tighter regulations, and rising input costs are making farming in California more difficult and, in some cases, less profitable. At the same time, pesticide pollution from farming is causing significant harm to California’s surface and groundwater, air quality, and human health. But there is a way to reduce pesticide use, protect the environment, and help farmers stay competitive according to a new report, Investing In Clean Agriculture: How California Can Strengthen Agriculture, Reduce Pollution And Save Money, published today by the Pacific Institute. “Business as usual isn’t working for our state,” declared Dr. Gary H. Wolff, author of the report and Principal Economist and Engineer with the Pacific Institute of Oakland, California. “Our plan will reduce pesticide use, protect public health, preserve the environment, and help California’s farmers stay competitive in a rapidly changing economy. We think this will be a win for consumers, a win for taxpayers, and a win for agriculture.” A US Geological Survey study of groundwater wells in the San Joaquin-Tulare Basin found at least one pesticide in 59 of 100 samples. But current efforts to reduce pesticide pollution are caught up in the courts. The rebate approach creates a voluntary incentive to reduce pesticide use while leaving it up to farmers to figure out the best way forward. “The Pacific Institute’s innovative proposal will reward farmers who are willing to learn about farming practices that protect water quality,” noted Leland Swenson of the Community Alliance With Family Farmers. “It is a voluntary and incentive-based way for farmers to respond to water quality regulations and keep pesticides out of drinking water.” The report describes how farmers can be rewarded for learning voluntarily about sustainable agricultural practices. A modest increase in the statewide “mill” fee, now levied on pesticides, is returned to farmers who take a short course on sustainable agriculture techniques and storm runoff management. This helps farmers stay competitive while reducing pesticide use – which will protect human health, preserve the environment, and eventually save taxpayers money by reducing medical costs. “Everybody wins if we can reduce our dependence on pesticides,” said Jonathan Kaplan of NRDC. “As the head of California’s Department of Pesticide Regulation just stated, ‘Integrated Pest Management is good for our economy as well as our environment’.” Investing In Clean Agriculture: How California Can Strengthen Agriculture, Reduce Pollution And Save Money estimates that the voluntary program and fee increase could bring $60 million per year into the agricultural sector while also bringing the most cutting edge research on sustainable farming techniques to those in the field.

Inyo County: Monitoring Groundwater Dependent Vegetation to Inform Groundwater Management

Nature Conservancy | August 1st, 1989

Inyo County and the City of Los Angeles have shown innovative and progressive leadership in the protection of groundwater dependent ecosystems in Owens Valley,

Inyo County and the City of Los Angeles have shown innovative and progressive leadership in the protection of groundwater dependent ecosystems in Owens Valley, and thanks to a landmark agreement between Inyo County and the Los Angeles Department of Water and Power (LADWP), the outlook for groundwater dependent ecosystems (GDEs) in this area is promising. In 1991, the Inyo/Los Angeles Long-Term Water Agreement (Agreement) established an elaborate system to manage groundwater pumping by LADWP to avoid substantial declines in groundwater dependent vegetation in the Owens Valley. Implemented to settle the County’s 1971 CEQA challenge of LADWP’s proposed method to fill its second aqueduct, the Agreement resolved years of litigation between the County and LADWP.

Irregular Focal Mechanisms Observed at Salton Sea Geothermal Field: Possible Influences of Anthropogenic Stress Perturbations

Stanford University | February 12th, 2018

At the Salton Sea Geothermal Field (SSGF), strain accumulation is released through seismic slip and aseismic deformation. Earthquake activity at the SSGF often oc

At the Salton Sea Geothermal Field (SSGF), strain accumulation is released through seismic slip and aseismic deformation. Earthquake activity at the SSGF often occurs in swarm-like clusters, some with clear migration patterns. We have identified an earthquake sequence composed entirely of focal mechanisms representing an ambiguous style of faulting, where strikes are similar but deformation occurs due to steeply-dipping normal faults with varied stress states. In order to more accurately determine the style of faulting for these events, we revisit the original waveforms and refine estimates of P and S wave arrival times and displacement amplitudes. We calculate the acceptable focal plane solutions using P-wave polarities and S/P amplitude ratios, and determine the preferred fault plane. Without constraints on local variations in stress, found by inverting the full earthquake catalog, it is difficult to explain the occurrence of such events using standard fault-mechanics and friction. Comparing these variations with the expected poroelastic effects from local production and injection of geothermal fluids suggests that anthropogenic activity could affect the style of faulting.

Irrigated agricultural adaptation to water and climate variability: The economic value of a water portfolio

Journal of Agricultural Economics (Wiley) | December 1st, 2014

Increasing aridity, more frequent and intense drought, and greater degrees of water scarcity create unique challenges for agriculture. In response to these challenges, wh

Increasing aridity, more frequent and intense drought, and greater degrees of water scarcity create unique challenges for agriculture. In response to these challenges, which often manifest themselves as lower and more variable surface water supplies, as well as depleted and degraded ground water supplies, growers tend to seek opportunities to adapt. One option for growers to reduce their exposure to water scarcity and heightened uncertainty is to diversify. Indeed, access to a portfolio of supplies is one way in which water and irrigation districts, as well as individual growers, are responding to the changing landscape of water resource availability. This article evaluates the benefits to irrigated agriculture from having access to multiple sources of water. With farm-level information on 1,900 agricultural parcels across California, we use the hedonic property value method to investigate the extent that growers benefit from having access to multiple sources of water (i.e., a water portfolio). Our results suggest that while lower quality waters, less reliable water, and less water all negatively impact agricultural land values, holding a water portfolio has a positive impact on land values through its role in mitigating the negative aspects of these factors and reducing the sensitivity of agriculture to climate-related factors. From a policy perspective, such results identify a valuable adaptation tool that irrigation districts may consider to help offset the negative impacts of climate change, drought, and population increases on water supply availability and reliability.