Adapting to Climate Change: Catching and Moving Water from Big Storms

California Department of Water Resources (DWR) | February 15th, 2024

Advanced Quantitative Precipitation Information: Improving Monitoring and Forecasts of Precipitation, Streamflow, and Coastal Flooding in the San Francisco Bay Area

American Meteorological Society (AMS) | October 26th, 2022

Advanced Quantitative Precipitation Information (AQPI) is a synergistic project that combines observations and models to improve monitoring and forecasts of precipitation

Advanced Quantitative Precipitation Information (AQPI) is a synergistic project that combines observations and models to improve monitoring and forecasts of precipitation, streamflow, and coastal flooding in the San Francisco Bay area. As an experimental system, AQPI leverages more than a decade of research, innovation, and implementation of a statewide, state-of-the-art network of observations, and development of the next generation of weather and coastal forecast models. AQPI was developed as a prototype in response to requests from the water management community for improved information on precipitation, riverine, and coastal conditions to inform their decision making processes. Observation of precipitation in the complex Bay Area landscape of California’s coastal mountain ranges is known to be a challenging problem. But, with new advanced radar network techniques, AQPI is helping fill an important observational gap for this highly populated and vulnerable metropolitan area. The prototype AQPI system consists of improved weather radar data for precipitation estimation; additional surface measurements of precipitation, streamflow and soil moisture; and a suite of integrated forecast modeling systems to improve situational awareness about current and future water conditions from sky to sea. Together these tools will help improve emergency preparedness and public response to prevent loss of life and destruction of property during extreme storms accompanied by heavy precipitation and high coastal water levels - especially high-moisture laden atmospheric rivers. The Bay Area AQPI system could potentially be replicated in other urban regions in California, the United States, and world-wide.

Advances in Sub-seasonal to Seasonal Prediction Relevant to Water Management in the Western United States

American Meteorological Society (AMS) | July 21st, 2022

Water management in the semi-arid western United States (U.S.) is a challenging endeavor that evolves from year to year based on large-scale atmospheric and oceanic condi

Water management in the semi-arid western United States (U.S.) is a challenging endeavor that evolves from year to year based on large-scale atmospheric and oceanic conditions. This region has frequently experienced prolonged periods of drought with substantial socioeconomic impacts; the most recent instance involves California entering its third consecutive drought year. As context for the economic implications of drought, California’s enacted state budget for the Fiscal Year 2021-22 authorizes more than $600 million for the California Department of Water Resources for providing immediate drought support to local water agencies (CA State Budget 2021a); this amount is part of a package of more than $5 billion over four years for water resilience and drought preparedness (CA State Budget 2021b). For drought preparedness, state and local water managers would like to rely on skillful forecasts on timescales that span the spectrum between weather forecasts and climate predictions. Despite recent improvements in developing sub-seasonal (2- to 6-weeks lead) and seasonal (2- to 6-months lead) prediction systems that compete with and/or outperform existing dynamical and statistical models (e.g., Gibson et al. 2021, Switanek et al. 2020, DeFlorio et al. 2019), forecasting limitations have hindered crucial management decisions for western U.S. water managers, especially related to longer-lead planning, budgeting, resource allocation, and better preparedness for wet and dry extremes (DeFlorio et al. 2021). Improved understanding of physical phenomena and processes governing weather and climate extremes and utilization of emerging forecast methodologies are critical to developing skillful S2S forecast products relevant to water management.

Advancing Stormwater Capture for Greener Schools in Los Angeles

Pacific Institute | August 15th, 2024

In communities across the United States, schools provide an enriching and safe environment for children to learn and grow. Yet urban schools, particularly those serving

In communities across the United States, schools provide an enriching and safe environment for children to learn and grow. Yet urban schools, particularly those serving under-resourced communities, are often covered in asphalt and offer little green space. The lack of shade, combined with intensely hot temperatures, can create dangerous conditions, with reports of asphalt reaching 140 degrees Fahrenheit and rubber surfaces reaching 165 degrees Fahrenheit (Klivans 2023). During heavy rains, runoff from these impervious surfaces floods and drains into the surrounding community. Climate change has exacerbated these impacts, leading to more extreme weather events, including hotter temperatures, severe droughts, and intense storms.

After the Flood: As the world’s largest dam removal takes shape, restoration ecologists are poised to transform a landscape

American Association for the Advancement of Science (AAAS) | October 19th, 2023

Standing on an outcrop of volcanic rock, Joshua Chenoweth looks across the languid waters of California’s Iron Gate Reservoir and imagines the transformation in store f

Standing on an outcrop of volcanic rock, Joshua Chenoweth looks across the languid waters of California’s Iron Gate Reservoir and imagines the transformation in store for the landscape. In early 2024, operators will open the floodgates on the 49-meter-high dam that blocks the Klamath River, allowing the more than 50 million tons of water it impounds to begin to drain. Once it’s gone, heavy equipment will dismantle the structure. All that will remain of the 11-kilometer-long reservoir that filled the valley for 60 years will be steep-sided slopes coated in gray mud, split once again by a free-flowing river.

Age Determination of the Remaining Peat in the Sacramento–San Joaquin Delta, California, USA

U.S. Geological Survey (USGS) | October 9th, 2007

The Sacramento–San Joaquin Delta of California was once a 1,400 square kilometer (km2) tidal marsh, which contained a vast layer of peat ranging up to 15 meters (m) thi

The Sacramento–San Joaquin Delta of California was once a 1,400 square kilometer (km2) tidal marsh, which contained a vast layer of peat ranging up to 15 meters (m) thick (Atwater and Belknap, 1980). Because of its favorable climate and highly fertile peat soils, the majority of the Delta was drained and reclaimed for agriculture during the late 1800s and early 1900s. Drainage of the peat soils changed the conditions in the surface layers of peat from anaerobic (having no free oxygen present) to aerobic (exposed to the atmosphere). This change in conditions greatly increased the decomposition rate of the peat, which consists largely of organic (plant) matter. Thus began the process of land-surface subsidence, which initially was a result of peat shrinkage and compaction, and later largely was a result of oxidation by which organic carbon in the peat essentially vaporized to carbon dioxide (Deverel and others, 1998; Ingebritsen and Ikehara, 1999). Because of subsidence, the land-surface elevation on farmed islands in the Delta has decreased from a few meters to as much as 8 m below local mean sea level (California Department of Water Resources, 1995; Steve Deverel, Hydrofocus, Inc., written commun., 2007). The USGS, in collaboration with the University of California at Davis, and Hydrofocus Inc. of Davis, California, has been studying the formation of the Delta and the impact of wetland reclamation on the peat column as part of a project called Rates and Evolution of Peat Accretion through Time (REPEAT). The purpose of this report is to provide results on the age of the remaining peat soils on four farmed islands in the Delta.

Agricultural Damages and Losses from ARkStorm Scenario Flooding in California

American Society of Civil Engineers (ASCE) | November 17th, 2016

Scientists designed the ARkStorm scenario to challenge the preparedness of California communities for widespread flooding with a historical precedence and increased l

Scientists designed the ARkStorm scenario to challenge the preparedness of California communities for widespread flooding with a historical precedence and increased likelihood under climate change. California is an important provider of vegetables, fruits, nuts, and other agricultural products to the nation. This study analyzes the agricultural damages and losses pertaining to annual crops, perennial crops, and livestock in California exposed to ARkStorm flooding. Statewide, flood damage is incurred on approximately 23% of annual crop acreage, 5% of perennial crop acreage, and 5% of livestock, e.g., dairy, feedlot, and poultry, acreage. The sum of field repair costs, forgone income, and product replacement costs span $3.7 and $7.1 billion (2009) for a range of inundation durations. Perennial crop loss estimates dominate, and the vulnerability of orchards and vineyards has likely increased with recent expansion. Crop reestablishment delays from levee repair and dewatering more than double annual crop losses in the delta islands, assuming the fragile system does not remain permanently flooded. The exposure of almost 200,000 dairy cows to ARkStorm flooding poses livestock evacuation challenges.

Amplification of downstream flood stage due to damming of fine-grained rivers

Nature Portfolio (Springer Nature) | June 1st, 2022

River dams provide many benefits, including flood control. However, due to constantly evolving channel morphology, downstream conveyance of floodwaters following dam clo

River dams provide many benefits, including flood control. However, due to constantly evolving channel morphology, downstream conveyance of floodwaters following dam closure is difficult to predict. Here, we test the hypothesis that the incised, enlarged channel downstream of dams provides enhanced water conveyance, using a case study from the lower Yellow River, China. We find that, although flood stage is lowered for small floods, counterintuitively, flood stage downstream of a dam can be amplified for moderate and large floods. This arises because bed incision is accompanied by sediment coarsening, which facilitates development of large dunes that increase flow resistance and reduce velocity relative to pre-dam conditions. Our findings indicate the underlying mechanism for such flood amplification may occur in >80% of fine-grained rivers, and suggest the need to reconsider flood control strategies in such rivers worldwide.

An assessment of future tidal marsh resilience in the San Francisco Estuary through modeling and quantifiable metrics of sustainability

Frontiers in Environmental Science (Frontiers) | November 25th, 2022

Quantitative, broadly applicable metrics of resilience are needed to effectively manage tidal marshes into the future. Here we quantified three metrics of temporal marsh

Quantitative, broadly applicable metrics of resilience are needed to effectively manage tidal marshes into the future. Here we quantified three metrics of temporal marsh resilience: time to marsh drowning, time to marsh tipping point, and the probability of a regime shift, defined as the conditional probability of a transition to an alternative super-optimal, suboptimal, or drowned state. We used organic matter content (loss on ignition, LOI) and peat age combined with the Coastal Wetland Equilibrium Model (CWEM) to track wetland development and resilience under different sea-level rise scenarios in the Sacramento-San Joaquin Delta (Delta) of California. A 100-year hindcast of the model showed excellent agreement (R2 = 0.96) between observed (2.86 mm/year) and predicted vertical accretion rates (2.98 mm/year) and correctly predicted a recovery in LOI (R2 = 0.76) after the California Gold Rush. Vertical accretion in the tidal freshwater marshes of the Delta is dominated by organic production. The large elevation range of the vegetation combined with high relative marsh elevation provides Delta marshes with resilience and elevation capital sufficiently great to tolerate centenary sea-level rise (CLSR) as high as 200 cm. The initial relative elevation of a marsh was a strong determinant of marsh survival time and tipping point. For a Delta marsh of average elevation, the tipping point at which vertical accretion no longer keeps up with the rate of sea-level rise is 50 years or more. Simulated, triennial additions of 6 mm of sediment via episodic atmospheric rivers increased the proportion of marshes surviving from 51% to 72% and decreased the proportion drowning from 49% to 28%. Our temporal metrics provide critical time frames for adaptively managing marshes, restoring marshes with the best chance of survival, and seizing opportunities for establishing migration corridors, which are all essential for safeguarding future habitats for sensitive species.

An evaluation of atmospheric rivers over the North Pacific in CMIP5 and their response to warming under RCP 8.5

American Geophysical Union (AGU) | November 13th, 2015

Landfalling atmospheric rivers over the North Pacific are evaluated in historical (1980–2005) simulations from 28 models participating in the fifth phase of the Couple

Landfalling atmospheric rivers over the North Pacific are evaluated in historical (1980–2005) simulations from 28 models participating in the fifth phase of the Coupled Model Intercomparison Project (CMIP5) and compared to the Modern-Era Retrospective Analysis for Research and Applications and ERA-Interim reanalyses. Landfalling dates are identified as having spatially elongated high wind and moisture features in physical proximity to the coastline. Model performance relative to reanalysis is found to be quite variable. The majority can resolve the spatial structure of landfalling events, but few correctly resolve the frequency distribution, interannual variability in number and amplitude of moisture flux, and median landfalling latitude. The response of a subset of high-performing models to projected warming at the end of the 21st century is investigated using Representative Concentration Pathway (RCP) 8.5 (2070–2100) projections. Selected models show a broadening of the frequency distribution, with the largest increase in frequency occurring equatorward of peak historical frequency. While there is a robust increase in AR-related moisture transport compared to the historical period, this increase is not linked to more extreme AR events within the context of the projected future climate. The occurrence of years with many AR dates is greater at the end of the 21st century than during the historical period. The equatorward increase in peak historical frequency is colocated with increases in the 850 and 250 hPa zonal winds. The response in moisture flux to warming is mostly thermodynamic, but equatorward of its peak distribution, it is dominated by a dynamic response.