A Basin-Scale Approach to Estimating Recharge in the Desert: Anza-Cahuilla Groundwater Basin, CA

American Water Resources Association (AWRA) | November 2nd, 2021

The Anza-Cahuilla groundwater basin located mainly in the semi-arid headwaters of the Santa Margarita River watershed in southern California is the principle source of g

The Anza-Cahuilla groundwater basin located mainly in the semi-arid headwaters of the Santa Margarita River watershed in southern California is the principle source of groundwater for a rural disadvantaged community and two Native American Tribes, the Ramona Band of Cahuilla and the Cahuilla. Groundwater in the study area is derived entirely from precipitation and managing groundwater sustainably requires an accurate assessment of the water balance components, yet long-term estimates do not exist. Demand for groundwater in the region has increased and groundwater quality has decreased due to population growth and increased irrigated cropland. To characterize monthly long-term natural recharge and runoff estimates, a physically-based water balance model (Basin Characterization Model) was locally calibrated and validated using nearby streamgages and published estimates of climatic and hydrologic variables. The average modeled annual recharge and runoff from 1981 to 2010 was 5.4 × 106 and 1.2 × 107 m3, respectively, for the study area. Recharge and runoff do not reliably occur in large amounts every year and recharge rarely occurs in the groundwater basin footprint. These long-term estimates can be used by water managers, stakeholders, and Native American Tribes to develop plans for sustainable management of future water resources, and as inputs to a three-dimensional groundwater model.

A Bayesian approach to infer nitrogen loading rates from crop and land-use types surrounding private wells in the Central Valley, California

European Geosciences Union (EGU) | May 7th, 2018

This study is focused on nitrogen loading from a wide variety of crop and land-use types in the Central Valley, California, USA, an intensively farmed region with high�

This study is focused on nitrogen loading from a wide variety of crop and land-use types in the Central Valley, California, USA, an intensively farmed region with high agricultural crop diversity. Nitrogen loading rates for several crop types have been measured based on field-scale experiments, and recent research has calculated nitrogen loading rates for crops throughout the Central Valley based on a mass balance approach. However, research is lacking to infer nitrogen loading rates for the broad diversity of crop and land use types directly from groundwater nitrate measurements. Relating groundwater nitrate measurements to specific crops must account for the uncertainty about and multiplicity in contributing crops (and other land uses) to individual well measurements, and for the variability of nitrogen loading within farms and from farm to farm for the same crop type. In this study, we developed a Bayesian regression model that allowed us to estimate land-use-specific groundwater nitrogen loading rate probability distributions for 15 crop and land-use groups based on a database of recent nitrate measurements from 2149 private wells in the Central Valley. The water and natural, rice, and alfalfa and pasture groups had the lowest median estimated nitrogen loading rates, each with a median estimate below 5 kg N ha -1 yr -1. Confined animal feeding operations (dairies) and citrus and subtropical crops had the greatest median estimated nitrogen loading rates at approximately 269 and 65 kg N ha -1 yr-1, respectively. In general, our probability-based estimates compare favorably with previous direct measurements and with mass-balance-based estimates of nitrogen loading. Nitrogen mass-balance-based estimates are larger than our groundwater nitrate derived estimates for manured and non-manured forage, nuts, cotton, tree fruit, and rice crops. These discrepancies are thought to be due to groundwater age mixing, dilution from infiltrating river water, or denitrification between the time when nitrogen leaves the root zone (point of reference for mass-balance derived loading) and the time and location of groundwater measurement.

A brief geologic and hydrologic reconnaissance of the Furnace Creek Wash area, Death Valley National Monument, California

U.S. Geological Survey (USGS) | July 1st, 1964

A call for strategic water-quality monitoring to advance assessment and prediction of wildfire impacts on water supplies

Frontiers in Water (Frontiers) | March 13th, 2023

Wildfires pose a risk to water supplies in the western U.S. and many other parts of the world, due to the potential for degradation of water quality. However, a lack of a

Wildfires pose a risk to water supplies in the western U.S. and many other parts of the world, due to the potential for degradation of water quality. However, a lack of adequate data hinders prediction and assessment of post-wildfire impacts and recovery. The dearth of such data is related to lack of funding for monitoring extreme events and the challenge of measuring the outsized hydrologic and erosive response after wildfire. Assessment and prediction of post-wildfire surface water quality would be strengthened by the strategic monitoring of key parameters, and the selection of sampling locations based on the following criteria: (1) streamgage with pre-wildfire data; (2) ability to install equipment that can measure water quality at high temporal resolution, with a focus on storm sampling; (3) minimum of 10% drainage area burned at moderate to high severity; (4) lack of major water management; (5) high-frequency precipitation; and (6) availability of pre-wildfire water-quality data and (or) water-quality data from a comparable unburned basin. Water-quality data focused on parameters that are critical to human and (or) ecosystem health, relevant to water-treatment processes and drinking-water quality, and (or) inform the role of precipitation and discharge on flow paths and water quality are most useful. We discuss strategic post-wildfire water-quality monitoring and identify opportunities for advancing assessment and prediction. Improved estimates of the magnitude, timing, and duration of post-wildfire effects on water quality would aid the water resources community prepare for and mitigate against impacts to water supplies.

A Case Study in Interstate Resource Management: The California-Nevada Water Controversy, 1865-1955

University of California, Davis (UC Davis) | May 1st, 1973

A changing framework for urban water systems

American Chemical Society (ACS) | May 8th, 2013

Urban water infrastructure and the institutions responsible for its management have gradually evolved over the past two centuries. Today, they are under increas

Urban water infrastructure and the institutions responsible for its management have gradually evolved over the past two centuries. Today, they are under increasing stress as water scarcity and a growing recognition of the importance of factors other than the cost of service provision are forcing a reexamination of long-held ideas. Research and development that supports new technological approaches and more effective management strategies are needed to ensure that the emerging framework for urban water systems will meet future societal needs

A Climatology of Narrow Cold-Frontal Rainbands in Southern California

American Geophysical Union (AGU) | January 27th, 2022

Narrow cold-frontal rainbands produce short-duration (<1-hr), high-intensity precipitation associated with flash floods and debris flows in Southern California, inclu

Narrow cold-frontal rainbands produce short-duration (<1-hr), high-intensity precipitation associated with flash floods and debris flows in Southern California, including the extremely destructive 2018 Montecito event. Prior research describes development, predictability, and associated hazards of these bands, though no known long-term record of their occurrence and climatological characteristics exists within the United States. This study provides the first known catalog of narrow coldfrontal rainbands during the winter seasons of 1995–2020 in Southern California, and explores characteristics of these features such as frequency, movement, and the large-scale meteorology that drives them. Events were documented manually using rain gauge observations, radar data, and output from atmospheric models. In total, 94 rainbands were documented during the study period, with an average of three landfalling events occurring in Southern California per water year. The intensity and impacts across the recorded events varied, though common weather patterns, including strengthening cyclones near the California coast, were associated with the documented events. This catalog supports weather-forecasting efforts as well as the future development of an automated detection algorithm.

A Commitment to Action: Advancing Integrated Water Management in California

California Department of Water Resources (DWR) | September 11th, 2013

This document highlights the key perspectives and recommendations that emerged during the Integrated Water Management Summit held in Sacramento on April 3, 2013.  The Ca

This document highlights the key perspectives and recommendations that emerged during the Integrated Water Management Summit held in Sacramento on April 3, 2013.  The California Department of Water Resources (DWR) hosted the event in partnership with the Water Education Foundation and the California Water Commission, and would like to thank the 200+ attendees and guest speakers who participated in the Summit. The goal of the Summit was to bring together water leaders from myriad agencies and organizations to share experiences and ideas on how we can effectively align to provide sustainable water resources services in the State, in the face of an uncertain future. Most agree that the water management approaches we have been relying on for several decades are no longer sustainable given today’s economic climate, our changing environment and the need to supply safe drinking water, agricultural water and flood protection for a growing population, while also protecting and enhancing valuable environmental resources.  The thoughtful presentations and informative discussions at the Summit served as an important milestone in the movement to shape a more cooperative and effective approach to water management in California. The Summit launched a new campaign called “Water 360” to help refocus and strengthen the collective efforts of California’s water management community by advancing integrated water management. Integrated water management is a framework for planning and implementation that melds the objectives of improving public safety, fostering environmental stewardship and supporting economic stability to lead to sustainable water resource management. Integrated water management is not a new concept in California, and great strides have been made in the last decade to utilize the approach, particularly at the regional level. The Water 360 Campaign builds on these early successes and calls for broader application across the entire state. DWR is prepared and committed to lead this effort in close partnership with other water leaders, particularly State, federal, and local agencies; and in collaboration with all stakeholders.

A Common Vision for the Colorado River System: Toward a Framework for Sustainability

Water and Tribes Initiative | October 5th, 2020

A Community Guide for Evaluating Future Urban Water Demand

Pacific Institute | August 31st, 2016

A Community Guide for Evaluating Future Urban Water Demand provides communities, environmental groups, ratepayer advocates, and anyone interested in sustainable water sup

A Community Guide for Evaluating Future Urban Water Demand provides communities, environmental groups, ratepayer advocates, and anyone interested in sustainable water supply planning with the knowledge and tools they need to understand water demand forecasts. Communities across the U.S. are faced with decisions about how to meet the needs of a growing population. To help make these decisions, water utilities often rely on forecasts that project water use 20 or 30 years into the future, consistent with the amount of time it takes to develop new supply infrastructure, such as desalination plants or reservoirs. For much of the 20th century, water use in American cities grew in proportion to population and the economy. Since the 1980s, however, water use in communities across the United States has remained steady or declined despite continued population and economic growth, due to improved water conservation and efficiency and structural changes in the American economy. While the water sector has undergone a fundamental transformation, the practice of water demand forecasting has been slow to keep pace. Water suppliers routinely overestimate future water demand based on often overstated estimates of population and economic growth and underestimates of the effects of water conservation and efficiency improvements. These inflated estimates of future water needs can result in unneeded water supply and treatment infrastructure, higher costs to ratepayers, and unnecessary environmental impacts. The guidebook explains how water utilities forecast long-term water demand and reviews some of the approaches and methods commonly used by utilities and consultants. It also provides a set of best practices that can be used to create more accurate and robust long-range water demand forecasts. Some of these best practices include accounting for water conservation and efficiency improvements and land use changes, as well as ensuring transparency and meaningful stakeholder engagement.