Updating the CALVIN Hydro-Economic Optimization Model of California: Central Valley Groundwater

University of California, Davis (UC Davis) | July 11th, 2012

Updates are being made to Central Valley groundwater in CALVIN, a hydro-economic model of California’s intertied water supply and delivery system. These updates reflect

Updates are being made to Central Valley groundwater in CALVIN, a hydro-economic model of California’s intertied water supply and delivery system. These updates reflect better estimates of water demands, groundwater availability, and local water management opportunities. This poster focuses on updating CALVIN groundwater parameters based on California Department of Water Resources’ (DWR) California Central Valley Groundwater-Surface Water Simulation Model (C2VSIM) and the United States Geological Survey (USGS) Central Valley Hydrologic Model (CVHM) model inputs and results. Two CALVIN update projects, using the DWR and USGS groundwater models, are underway to improve groundwater representation including basin inflows, reuse, return flows, capacities, and pumping costs. These sub-projects will result in a CALVIN model with updated groundwater representation based on C2VSIM and CVHM. This poster shows a preliminary comparison of these sub-projects and a summary comparison between the DWR and USGS models.

Urban Water Demand in California to 2100: Incorporating Climate Change

Pacific Institute | August 28th, 2012

Climate change will have significant impacts in California not just on water supply, but also on water demand. A new, free tool from the Pacific Institute* helps water

Climate change will have significant impacts in California not just on water supply, but also on water demand. A new, free tool from the Pacific Institute* helps water managers to forecast urban water demand with four global climate change models and compare different possible futures to the year 2100 by altering greenhouse gas emissions, population projections, conservation and efficiency measures, and more. The research shows climate change will cause increased water use in California’s cities and suburbs, even as water supply is expected to diminish. Urban water use – residential plus commercial, industrial, and institutional uses – accounts for over 20% of the water use in California, and up to half of urban water use is outdoors. The new report Urban Water Demand in California to 2100: Incorporating Climate Change describes how warming due to climate change is causing increases in water demand for landscapes, and will continue to drive up future water demand, particularly as more Californians settle in warmer, drier inland areas. The Pacific Institute ran a number of scenarios through 2100. The analysis finds that climate change alone could increase urban water demand in 2100 by 8% percent, or around 1 million acre-feet, under a medium-high greenhouse gas emissions scenario. That is the amount of water needed to satisfy the current household needs of 6.7 million Californians. “A million acre-feet of water is significant, and, of course, climate is not the only driver affecting demand. But factoring levels of climate change into the mix is critical,” said Dr. Juliet Christian-Smith of the Pacific Institute Water Program. “Future water use in California depends on a range of factors – technological, political, and economic – many of which are uncertain, but water utilities still need to plan. We created a flexible modeling tool that allows users to run their own scenarios, comparing how a range of factors in a range of climate change scenarios is likely to affect future patterns of water use in their specific areas.”

Use of a Three-Dimensional Model for the Analysis of the Ground-Water Flow System in Parker Valley, Arizona and California

U.S. Geological Survey (USGS) | December 1st, 1982

Use of Radiocarbon Ages to Narrow Groundwater Recharge Estimates in the Southeastern Mojave Desert, USA

Hydrology (MDPI) | September 13th, 2018

Estimating groundwater recharge in arid or semiarid regions can be a difficult and complex task, since it is dependent on a highly variable set of spatial and temporal h

Estimating groundwater recharge in arid or semiarid regions can be a difficult and complex task, since it is dependent on a highly variable set of spatial and temporal hydrologic parameters and processes that are dependent on the local climate, the land surface properties, and subsurface characteristics. As a result, traditional methods for estimating the recharge can result in a wide range of derived values. This is evident in the southeastern Mojave Desert, where calculated recharge estimates by previous investigators that range over an order of magnitude (from ~2500 to ~37,000 acre feet per year) are reported. To narrow down this large span of recharge estimates to narrower and more plausible values, this study evaluates the previous recharge estimates in this region, to examine the sources of variability in the reported results and to constrain the recharge estimates based on the hydrologic conditions and the radiocarbon age-dating of spring flows—even without knowledge of the precise subsurface hydrology. The groundwater age and perennial flow characteristics of springs in this study could not be derived from waters sourced solely from local recharge. Therefore, the springs in this study require a significant groundwater contribution to their overall discharge. A previously described conceptual site model in the region established that Bonanza Spring is similarly hydrologically connected to the regional basin-fill aquifer, based on geologic and geochemical/isotopic analyses, and this conceptual site model for where perennial spring water is sourced should readily be extended to these other perennial springs in this region.

User Manual for the California Central Valley Groundwater-Surface Water Simulation Model

California Department of Water Resources (DWR) | June 13th, 2013

This report describes the input and output files for the California Central Valley Groundwater-Surface Water Simulation Model (C2VSim). C2VSim is an integrated numeri

This report describes the input and output files for the California Central Valley Groundwater-Surface Water Simulation Model (C2VSim). C2VSim is an integrated numerical model simulating land surface processes and groundwater and surface water flows in the main alluvial aquifer system of California’s Central Valley (figure 1). C2VSim was developed using the Integrated Water Flow Model (IWFM) application, which couples a three-dimensional finite element groundwater simulation process with one-dimensional land surface, stream flow, lake, unsaturated zone and smallstream watershed simulation processes. The C2VSim version described in this report runs under IWFM version 3.02 and utilizes a coarse grid, and is thus referred to as version 3.02-CG. In addition, the input files for the C2VSim model are regularly updated to correct errors, incorporate improved input data or extend the simulation time period. These updates are referred to as revisions; this report describes the data in revision R374, released in June 2013. The C2VSim model inputs include monthly historical precipitation, stream inflows, surface water diversions, land use and crop acreages for the simulation period, October 1921 through September 2009. C2VSim dynamically calculates crop water demands, allocates contributions from precipitation, soil moisture and surface water diversions, and calculates the groundwater pumpage required to meet the remaining demand. The coarse grid version of the C2VSim model incorporates a finite element grid with 1392 elements, grouped into 21 water budget subregions (figure 1), which are further grouped by drainage basin into five hydrologic regions. The model subregions are based on Depletion Study Areas (DSAs), originally created by the DWR Division of Planning for estimating regional water supplies and demands. Hydrologic parameters (including hydraulic conductivities, storage parameters and recession coefficients) were calibrated to match observed values including groundwater heads, groundwater head differences between well pairs, surface water flows, and stream-groundwater flows for the period between September 1975 and October 2003. The model simulates the historical response of the Central Valley’s groundwater flow system to historical stresses, and can also be used to simulate the response to projected future stresses. Agricultural groundwater pumping is not monitored in the Central Valley, and the C2VSim model provides pumpage estimates that are considered robust because they are constrained spatially and temporally by the estimated demand and surface water supplies. The calibrated model is also being used as the basis for the groundwater flow component of CalSim 3, a water resources planning model for simulating operation of the California State Water Project (SWP) and Federal Central Valley Project (CVP).

User’s Manual for the Draper Climate-Distribution Software Suite with Data-Evaluation Tools

U.S. Geological Survey (USGS) | March 20th, 2019

Development of a time series of spatially distributed climate data is an important step in the process of developing physically based environmental models requiri

Development of a time series of spatially distributed climate data is an important step in the process of developing physically based environmental models requiring distributed inputs of climate data beyond what is available from observations collected at climate stations. To prepare inputs required for model-mapping units across the study area, climate data (temperature and precipitation) are distributed by combining data from gridded surfaces of mean-monthly climate-data values with (often) widely spaced daily pointobservations. Examples of climate-data files used to develop PRMS-formatted input files for the Merced River Basin Precipitation-Runoff Modeling System (PRMS) are includedin this manual. The Draper Climate-Distribution Software Suite (Draper Suite) consists of the Draper climate-distribution program (Draper) and several supporting pre- and post-processing applications. Draper combines spatially distributed input in the form of monthly averaged values for precipitation, maximum temperature, and minimum temperature with daily observed data from climate stations to estimate distributed climate-data values at predefined locations across a study area (typically adrainage basin) on a daily time step. Alternative methods are used when station data are limited or missing for a particular day. Draper uses a set of required and optional input andoutput files with defined formats and naming conventions. Ashell application also is available to manage multiple runs of the Draper application. Other applications in the Draper Suite include (1) a toolto find and interactively remove outliers in the input data, (2) atool to check and enforce a minimum daily temperature range, and (3) a tool to view output diagnostic information as time- series graphs. These tools can be used iteratively to evaluate and improve the results from Draper as part of a work flow involving physically-based environmental models, such as the Precipitation-Runoff Modeling System (PRMS).

Using Conceptual Models and Decision-Support Tools to Guide Ecosystem Restoration Planning and Adaptive Management: An Example from the Sacramento–San Joaquin Delta, California

University of California, Davis (UC Davis) | October 1st, 2012

The Sacramento–San Joaquin Delta (the Delta) is located on the western edge of California’s Central Valley and is of critical ecological and economic importance. H

The Sacramento–San Joaquin Delta (the Delta) is located on the western edge of California’s Central Valley and is of critical ecological and economic importance. However, ecosystem alterations for human uses changed many of the Delta’s natural processes, and it is now considered in need of restoration. An approach was developed to evaluate and rank restoration actions in the Delta under the Ecosystem Restoration Program’s Delta Regional Ecosystem Restoration Implementation Plan (DRERIP). The DRERIP approach provides an explicit framework for evaluating restoration actions, using linked conceptual models, an action evaluation procedure, and a decision-support tool. Conceptual models allow scientists and managers to synthesize scientific information and make qualitative predictions about ecosystem function and restoration outcomes to guide and focus restoration efforts. The action evaluation procedure is a structured assessment of restoration actions. The procedure clearly describes actions to be evaluated, assesses the magnitude (importance and scale) and certainty of anticipated ecological outcomes, estimates degrees of worth (achieving intended outcomes) and risk (causing adverse consequences), evaluates the reversibility of the action, and identifies opportunities for learning. The values for worthiness, risk, reversibility, and learning opportunity are used in the decision- support tool to determine the fate of a proposed action. The decision-support tool is a structured decision tree that determines the disposition of an action: whether a restoration project should be discarded, revised with a different approach and re-evaluated, or implemented; and, if implemented, at what scale (targeted research, pilot project, or full implementation). The DRERIP approach provides managers with a valuable tool for restoration planning, and a foundation for integration with quantitative methods for a comprehensive ecosystem restoration plan.

Valuing the benefits of forest restoration on enhancing hydropower and water supply in California's Sierra Nevada

Science of the Total Environment (Elsevier) | March 15th, 2023

Forest restoration through mechanical thinning, prescribed burning, and other management actions is vital to improving forest resilience to fire and drought across the We

Forest restoration through mechanical thinning, prescribed burning, and other management actions is vital to improving forest resilience to fire and drought across the Western United States, and yields benefits that can be monetized, including improvements in water supply and hydropower. Using California's Sierra Nevada as a study area, we assess the water and energy benefits of forest-restoration projects. By using a scalable top-down approach to track annual evapotranspiration following forest disturbance, coupled with hydropower simulations that include energy-price information, and marginal prices for water sales, we project the potential economic benefits of hydropower and water sales accruing to water-rights holders. The results found that water-related benefits from strategically planned fuels-reduction treatments now being carried out can be sufficient to offset costs of management actions aimed at forest restoration, especially in the face of climate change. Our findings justified investments in restoring forests and reinforce the central role of water and hydropower providers in partnerships for management of source-water watersheds. Results also highlighted the importance of accurate, scalable data and tools from the hydrology and water-resources community.

Variability and Trends in Precipitation, Temperature and Drought Indices in the State of California

Hydrology (MDPI) | March 28th, 2016

This study presents a comprehensive assessment of the variability and trends of the precipitation and temperature along with the trends in drought indices over the State

This study presents a comprehensive assessment of the variability and trends of the precipitation and temperature along with the trends in drought indices over the State of California. The non-parametric Mann–Kendall trend test is applied with a trend-free pre-whitening procedure in trend identification. A dataset containing 120-year (water years 1896–2015) monthly precipitation, average temperature, maximum temperature, minimum temperature and the Palmer Index for seven climatic regions of the state is used for this purpose. The results confirm previous work indicating that no clear trends are observed in precipitation, while a distinct warming trend is evident in temperature over the state. New findings of this study include: (1) in general, the variability of annual, winter (December–February) and spring (March–May) precipitation shows an increasing tendency, implying intensified frequency of the occurrence of dry or wet extremes; (2) on the annual scale and in the summer, statewide meteorological, hydrological and agricultural drought indices all have decreasing trends, indicating the more frequent occurrence of drought events; and (3) among seven regions, the South Coast Drainage region generally has the most significant warming trend, as well as the most significant declining trends in drought indices. Overall, these findings are highly meaningful from both theoretical and practical perspectives, in the context of providing critical information in developing prediction models and guiding water resources management practices, respectively.

Ventura Regional Groundwater Flow Model and Updated Hydrogeologic Conceptual Model: Oxnard Plain, Oxnard Forebay, Pleasant Valley, West Las Posas, and Mound Groundwater Basins

United Water Conservation District (UWCD) | July 2nd, 2018

United Water Conservation District’s (United) effort of the past six years to develop a significantly improved groundwater flow model for the Oxnard Plain and adjacent

United Water Conservation District’s (United) effort of the past six years to develop a significantly improved groundwater flow model for the Oxnard Plain and adjacent basins, as described in this report, is part of a broader effort by United and other agencies in the region to better understand the key factors that affect availability and usability of our area’s groundwater resources. Use of these resources, which have been supplemented for the past 90 years by spreading (artificial recharge) of surface water diverted from the Santa Clara River, has been key to the past growth and the future sustainability of cities and agriculture on the Oxnard coastal plain. Groundwater of suitable quality for a wide range of beneficial uses can be withdrawn from wells and delivered to cities or farms on the Oxnard coastal plain and in the Santa Clara River valley without construction of extensive, costly infrastructure projects (such as the aqueducts and surface reservoirs of the State Water Project), and provides a reliable water supply and resilience against potential major disruptions such as earthquakes and droughts. Although imported surface water from northern California began contributing significantly to the region’s municipal water-supply portfolio over the past half century, and desalination of brackish water or seawater may play an important water-supply role for the region in the future, neither of these alternative sources of water-supply can match the low cost and small environmental footprint of the existing groundwater resources, as enhanced by United’s recharge operations. Unfortunately, the relative accessibility, reliability, and low cost of groundwater for water supply has resulted in it being extracted from the aquifers underlying the Oxnard coastal plain at a faster rate than it has been replenished over the long term. This “overdraft” has resulted in corresponding groundwater-level declines in regional aquifers that have only been partly reversed during wet climatic cycles. In turn, these groundwater-level declines have resulted in seawater intrusion into the regional aquifers near the coast (since the 1930s), and could potentially exacerbate other water-quality problems or cause subsidence of land surface if allowed to continue. United coordinated with other regional water-supply stakeholders to plan and implement major projects in the 1950s, 1980s, and 1990s to mitigate the effects of overdraft, and these efforts have been partially successful. However, under California’s Sustainable Groundwater Management Act (SGMA) of 2015, groundwater sustainability plans (GSPs) must be developed and implemented by 2020 to provide long-term solutions that will prevent further negative impacts in “critically overdrafted basins,” including the Oxnard Plain and Pleasant Valley basins, and by 2022 for other groundwater basins in United’s service area. The geometry and physical characteristics of the aquifers, combined with the interactions of the stresses acting on those aquifers, within the regional groundwater basins are complex. The complexity is compounded by spatial and temporal variability of groundwater recharge and discharge. In order to forecast the effects of potential future water-supply alternatives with a sufficient level of certainty to evaluate and design new projects, it became evident to United in 2011 that the region needed a numerical groundwater-flow model that could discretely simulate each of the seven individual aquifer systems and six intervening aquitards that comprise the multi-layered regional aquifer system beneath the Oxnard and Pleasant Valley groundwater basins. The California Department of Water Resources notes that “while models are, by definition, a simplification of a more complex reality, they have proven to be useful tools over several decades for addressing a range of groundwater problems and supporting the decision-making process. Models can be useful tools for estimating the potential hydrologic effects of proposed water management activities” (Joseph and others, 2016). Numerical models of local groundwater basins developed by California Department of Water Resources in the 1970s, and by the U.S. Geological Survey in the 1990s, were useful for answering the questions about groundwater being asked at those times. However, these models assumed a greatly simplified hydrologic system, consisting of one, two, or three “lumped” aquifers, rather than explicitly modeling the seven aquifers (and six aquitards) that actually exist in the region. This oversimplification was necessary at the time due to limitations in available data, as well as limitations in computer processing power. Consequently, these models produced simulated groundwater elevations that did not always match measured groundwater elevations very well in some key areas, including near the coast and in recharge zones, reducing the reliability and increasing the uncertainty of forecasts for future conditions. Therefore, in 2012 United initiated, with financial and technical support from regional stakeholders, development of the numerical model described in this report (“Ventura Regional Groundwater Flow Model,” or VRGWFM), which discretely simulates each aquifer and aquitard underlying the Oxnard coastal plain as a distinct “layer” (in modeling terminology). The goal of this effort is to achieve significant improvement in calibration compared to previous models, allowing simulation of a greater range of natural and man-made hydrogeologic processes that have occurred in the past, and thereby increase the reliability of model predictions for the future. That said, the California Department of Water Resources warns, “there should be no expectation that a single ‘true’ model exists. All models and model results will have some level of uncertainty” (Joseph and others, 2016). For this reason, United is committed to continuous improvement of the VRGWFM as new data and improved methods become available, to minimize potential uncertainty. United would like to acknowledge the financial support provided by the Fox Canyon Groundwater Management Agency (FCGMA) and the Santa Clara River Watershed Committee, as well as the technical input and assistance provided by the FCGMA Technical Advisory Group (TAG), the Calleguas Municipal Water District’s technical staff and consultants, and the participants of the Expert Panel convened by United to review and provide guidance for improving the model (Dr. Sorab Panday, James Rumbaugh, and John Porcello). United would also like to acknowledge the various water and sanitation districts (including Ventura County Watershed Protection District), municipalities, and individuals that provided data to support development of the VRGWFM. We especially want to acknowledge the importance of the U.S. Geological Survey effort in the 1990s and 2000s to establish a regional groundwater monitoring-well network and construct the first MODFLOW model for the basins underlying the entire Santa Clara River and Calleguas Creek watersheds; their model was a critical “jumping-off point” for the VRGWFM. Finally, United’s Groundwater Department staff would like to recognize the foresight and patience of United’s Board of Directors, previous and present General Managers, and—most notably—former Groundwater Department Manager Tony Morgan, for their efforts in kicking off this modeling effort six years ago and guiding/pushing staff to completion of “Version 1.0” today.