Changes in Evapotranspiration of Agricultural Crops in Kern County during the 2014-2015 Drought Years

University of California, Davis (UC Davis) | September 5th, 2017

The 2012-2015 drought in California has major impacts for agricultural water users in Kern County. Farmers shifted crop planting patterns and irrigation scheduling to min

The 2012-2015 drought in California has major impacts for agricultural water users in Kern County. Farmers shifted crop planting patterns and irrigation scheduling to minimize profit loss with water shortage. This report models the changes in crop evapotranspiration from 2011 to 2014 and 2015 using the remote-sensing-based METRIC model developed by the University of Idaho. Results show that rather than universal losses of acreage and productivity, farmers reduced acreage on annual crops while increasing acreage on low-water-use new orchards. Productivity increased on the annual crops that remained in production, perhaps due to fallowing less productive land. High-value crops such as citrus and grapes saw increases in both acreage and productivity. Remote-sensing-based evapotranspiration mapping provides an important tool to policymakers by providing field-based estimates of a wide range of farmer responses to drought including planting, fallowing, under-irrigation, and, if combined with productivity models, changes in revenue. 

Changes in the productivity of US West Coast fish stocks

Fisheries Research (Elsevier) | April 21st, 2023

The California Current ecosystem is highly dynamic at interannual to interdecadal time scales. Variability has been documented in pelagic and other fish species, but clim

The California Current ecosystem is highly dynamic at interannual to interdecadal time scales. Variability has been documented in pelagic and other fish species, but climate change may be altering the historical models of variation. This study investigates changes in productivity of 31 fish stocks in the California Current ecosystem. Productivity was measured from recent stock assessments, as the per-capita recruitment rate, estimated with a dynamic stock-recruitment model. Contrary to expectations, the dynamic stock-recruitment model fit better than the corresponding stationary model for only seven of the 31 stocks. There was little evidence of linear drift in productivity that might be expected to result from climate change. Climate variables improved forecast accuracy for a few stocks, but there was no common climate signal in productivity. One explanation of these results is that most of the west coast stocks are above their biomass levels for maximum sustainable yield, making them less susceptible to environmental variation. On the other hand, the dynamic recruitment models improved short-term forecasts for all stocks, which may be useful for quota setting. Finally, results for the subset of stocks with dynamic recruitment models could be used to establish dynamic biological reference points.

Changes in water consumption linked to heavy news media coverage of extreme climatic events

American Association for the Advancement of Science (AAAS) | October 25th, 2017

Public awareness of water- and drought-related issues is an important yet relatively unexplored component of water use behavior. To examine this relationship, w

Public awareness of water- and drought-related issues is an important yet relatively unexplored component of water use behavior. To examine this relationship, we first quantified news media coverage of drought in California from 2005 to 2015, a period with two distinct droughts; the later drought received unprecedentedly high media coverage, whereas the earlier drought did not, as the United States was experiencing an economic downturn coinciding with a historic presidential election. Comparing this coverage to Google search frequency confirmed that public attention followed news media trends. We then modeled single-family residential water consumption in 20 service areas in the San Francisco Bay Area during the same period using geospatially explicit data and including news media coverage as a covariate. Model outputs revealed the factors affecting water use for populations of varying demographics. Importantly, the models estimated that an increase of 100 drought-related articles in a bimonthly period was associated with an 11 to 18% reduction in water use. Then, we evaluated high-resolution water consumption data from smart meters, known as advanced metering infrastructure, in one of the previously modeled service areas to evaluate breakpoints in water use trends. Results demonstrated that whereas nonresidential commercial irrigation customers responded to changes in climate, single-family residential customers decreased water use at the fastest rate following heavy drought-related news media coverage. These results highlight the need for water resource planners and decision makers to further consider the importance of effective, internally and externally driven, public awareness and education in water demand behavior and management.

Changes in Winter Atmospheric Rivers along the North American West Coast in CMIP5 Climate Models

American Meteorological Society (AMS) | April 1st, 2014

Most extreme precipitation events that occur along the North American west coast are associated with winter atmospheric river (AR) events. Global climate models h

Most extreme precipitation events that occur along the North American west coast are associated with winter atmospheric river (AR) events. Global climate models have sufficient resolution to simulate synoptic features associated with AR events, such as high values of vertically integrated water vapor transport (IVT) approaching the coast. From phase 5 of the Coupled Model Intercomparison Project (CMIP5), 10 simulations are used to identify changes in ARs impacting the west coast of North America between historical (1970–99) and end-of-century (2070–99) runs, using representative concentration pathway (RCP) 8.5. The most extreme ARs are identified in both time periods by the 99th percentile of IVT days along a north–south transect offshore of the coast. Integrated water vapor (IWV) and IVT are predicted to increase, while lower- tropospheric winds change little. Winter mean precipitation along the west coast increases by 11%–18% [from 4% to 6% (8C)21], while precipitation on extreme IVT days increases by 15%–39% [from 5% to 19% (8C)21]. The frequency of IVT days above the historical 99th percentile threshold increases as much as 290% by the end of this century.

Characterizing and quantifying nutrient sources, sinks and transformations in the Delta: synthesis, modeling, and recommendations for monitoring

San Francisco Estuary Institute (SFEI) | January 5th, 2016

The Sacramento-San Joaquin Delta (the Delta) receives high loads of the nutrients nitrogen (N) and phosphorous (P) from wastewater treatment effluent and agricultural run

The Sacramento-San Joaquin Delta (the Delta) receives high loads of the nutrients nitrogen (N) and phosphorous (P) from wastewater treatment effluent and agricultural runoff. Flows from the Sacramento River, San Joaquin River, and other tributaries transport these loads through a complex network of rivers, channels and flooded islands, before entering San Francisco Bay. Excessive loads of N and P can adversely impact ecosystem health by causing excessive algal blooms and low dissolved (Valiela et al, 1992; Kamer and Stein 2003). Excessive nutrients may also contribute to the occurrence of harmful algal blooms (Bates et al, 1989) and overgrowth of nuisance aquatic macrophytes (Valiela et al, 1992). Major nutrient management decisions are being considered in both the Delta and San Francisco Bay, and those decisions require the best-available science to understand the factors that regulate ambient conditions, and the effects of loads and ambient conditions on ecosystem health. A mechanistic and quantitative understanding of nutrient cycling and fate in the Delta is essential both for informed decisions related to current conditions and also because of major anticipated changes in both loads to the Delta (upgrades at wastewater treatment facilities) and habitat function due to restoration efforts and water management. We hypothesized that the Delta is an important biogeochemical reactor, and that transformations or losses strongly regulate ambient nutrient concentrations within the Delta and modulate nutrient loads to San Francisco Bay. Both N and P have complex cycles and require careful investigation. In this paper, we focus on nitrogen, including loads, cycling, and losses or transformations that influence its ultimate fate.

Characterizing changes in streamflow and sediment supply in the Sacramento River basin, California, using hydrological simulation program

Water, Multidisciplinary Digital Publishing Institute (MDPI) | September 30th, 2016

A daily watershed model of the Sacramento River Basin of northern California was developed to simulate streamflow and suspended sediment transport to the San Francisco B

A daily watershed model of the Sacramento River Basin of northern California was developed to simulate streamflow and suspended sediment transport to the San Francisco Bay-Delta. To compensate for sparse data, a unique combination of model inputs was developed, including meteorological variables, potential evapotranspiration, and parameters defining hydraulic geometry. A slight decreasing trend of sediment loads and concentrations was statistically significant in the lowest 50% of flows, supporting the observed historical sediment decline. Historical changes in climate, including seasonality and decline of snowpack, contribute to changes in streamflow, and are a significant component describing the mechanisms responsible for the decline in sediment. Several wet and dry hypothetical climate change scenarios with temperature changes of 1.5 C and 4.5 C were applied to the base historical conditions to assess the model sensitivity of streamflow and sediment to changes in climate. Of the scenarios evaluated, sediment discharge for the Sacramento River Basin increased the most with increased storm magnitude and frequency and decreased the most with increases in air temperature, regardless of changes in precipitation. The model will be used to develop projections of potential hydrologic and sediment trends to the Bay-Delta in response to potential future climate scenarios, which will help assess the hydrological and ecological health of the Bay-Delta into the next century.

Characterizing storm-induced coastal change hazards along the United States West Coast

Nature Portfolio (Springer Nature) | May 23rd, 2022

Traditional methods to assess the probability of storm-induced erosion and flooding from extreme water levels have limited use along the U.S. West Coast where swell domin

Traditional methods to assess the probability of storm-induced erosion and flooding from extreme water levels have limited use along the U.S. West Coast where swell dominates erosion and storm surge is limited. This effort presents methodology to assess the probability of erosion and flooding for the U.S. West Coast from extreme total water levels (TWLs), but the approach is applicable to coastal settings worldwide. TWLs were derived from 61 years of wave and water level data at shore-perpendicular transects every 100-m along open coast shorelines. At each location, wave data from the Global Ocean Waves model were downscaled to the nearshore and used to empirically calculate wave run-up. Tides were simulated using the Oregon State University’s tidal data inversion model and non-tidal residuals were calculated from sea-surface temperature and pressure anomalies. Wave run-up was combined with still water levels to generate hourly TWL estimates and extreme TWLs for multiple return periods. Extremes were compared to onshore morphology to determine erosion hazards and define the probability of collision, overwash, and inundation.

Characterizing the spatial scales of extreme daily precipitation in the United States

American Meteorological Society (AMS) | October 1st, 2018

The spatial extent of an extreme precipitation event can be important for a basin’s hydrologic response and subsequent flood risk, and may yield insights into underlyi

The spatial extent of an extreme precipitation event can be important for a basin’s hydrologic response and subsequent flood risk, and may yield insights into underlying atmospheric processes. Using a relaxed movingneighborhood approach, we develop indicator semivariograms based on precipitation records from the Global Historical Climatology Network–Daily (GHCN-D) station network to directly quantify the climatological length scales of extreme daily precipitation over the United States during 1965–2014. We find that the length scales of extreme (90th percentile) daily precipitation events vary both regionally and seasonally. Over the eastern half of the United States, daily extreme precipitation length scales reach 400 km during the winter months, but are approximately half as large during the summer months. The Northwest region, on the other hand, exhibits little seasonal variation, with extreme precipitation length scales of approximately 150 km throughout the year. By leveraging in situ station measurements, our study avoids some of the uncertainties associated with satellite or interpolated precipitation data, and provides the longest climatological assessment of length scales of extreme daily precipitation over the United States to date. Although the length scales that we calculate can be sensitive to station density, neighborhood size, and neighborhood relaxation, we find that the interregional and inter-seasonal differences in length scales are relatively robust. Our method could be extended to quantify changes in the spatial extent of extreme daily precipitation in the recent past, and to investigate the underlying causes of any changes that are detected.

Climate and choice in the Colorado River Basin

Agricultural & Applied Economics Association (AAEA) | October 31st, 2024

Climate Change Analysis for the Santa Ana River Watershed

U.S. Bureau of Reclamation (USBR) | September 24th, 2013

The Santa Ana Watershed Basin Study (Basin Study) is a collaborative effort by the Santa Ana Watershed Project Authority (SAWPA) and the Bureau of Reclamation (Reclamatio

The Santa Ana Watershed Basin Study (Basin Study) is a collaborative effort by the Santa Ana Watershed Project Authority (SAWPA) and the Bureau of Reclamation (Reclamation), authorized under the Sustain and Manage America's Resources for Tomorrow SECURE Water Act (Title IX, Subtitle F of Public Law 111-11). The study began in 2011 and was completed in the spring of 2013. The Basin Study complements SAWPA’s Integrated Regional Water Management (IRWM) planning process, also known as the “One Water One Watershed” (OWOW) Plan, and refines the watershed’s water projections, and identifies potential adaptation strategies, in light of projected effects of climate change. This climate change analysis for the Santa Ana River Watershed (SARW) is a contributing section to the Basin Study. This report explains the methods used to develop an analysis of potential implications of the changing climate, and how those implications might affect issues of importance to the Santa Ana River Watershed. Chapter 1 provides an introduction to the project and the study area, along with a summary of relevant previous studies. The development of climate projections and hydrology models used can be found in Chapter 2. Chapter 3 provides projections for water supply and demand in the SARW. An impact analysis was conducted focusing on key areas of importance to the SARW, the results of which can be found in Chapter 4. A tool to evaluate demand management is presented in Chapter 5, along with a case study of potential adaptation strategies. Chapter 6 addresses uncertainties in climate change analysis. In light of climate change, prolonged drought conditions, growth, and population projections, a strong concern exists to ensure there will be adequate water supplies to meet future water demand. The findings of this Basin Study will be used to update the OWOW Plan, evaluate the implications of climate change, assess increased energy demand, and ensure that future water quality and supply needs are met. Goals of the study include: incorporating existing regional and local planning studies within the watershed; sustaining the innovative “bottom up” approach to regional water resources management planning; ensuring an integrated, collaborative approach; using science and technology to assess climate change and greenhouse emissions effects; facilitating watershed adaptation planning; and expanding outreach to all major water uses and stakeholders. Future water supply was analyzed for the Santa Ana River Watershed using the Variable Infiltration Capacity (VIC) hydrologic model (Liang et al., 1994; Liang et al., 1996; Nijssen et al., 1997) to project streamflow using 112 different projections of future climate. Projected climate variables, including daily precipitation, minimum temperature, maximum temperature, and wind speed, came from the Bias Corrected and Spatially Downscaled Coupled Model Intercomparison Project Phase 3 (BCSD-CMIP3) archive. Historical VIC model simulations over the period 1950-1999 were conducted using historical meteorological forcings (factors affecting the climate of the earth that drive or “force” the climate to change) developed by Maurer et al., (2002), and subsequent extensions. The VIC hydrologic model solves the water balance for each of a series of 1/8° by 1/8° (~12km x 12 km) grid cells, which represent the watershed. Daily climate projections span the time period January 1, 1950 to December 31, 2099 and exist for each grid cell. Grid based outputs of daily runoff and baseflow generated by the VIC hydrologic model are routed to select sites throughout the watershed to produce daily streamflow projections. Through coordination with SAWPA and local water agencies, 36 key locations in the basin were determined, so that sub-basins could be delineated. Change factors were developed by calculating decade mean (reference decade – 1990s; three future decades – 2020s, 2050s, and 2070s) total precipitation and temperature, then calculating percent change, and finally calculating the median change for all the 112 projections. Final products include data sets at key locations for precipitation, temperature, evapotranspiration, April 1st Snow Water Equivalent (SWE), and streamflow. These data sets were used to answer frequently asked questions regarding impacts of climate change on the Santa Ana River Watershed.