Projects Worked On
The Middle East and North Africa have longstanding water supply and sanitation challenges. In 2011, US Agency for International Development (USAID) partnered with Development Alternatives Inc. to end the global freshwater crisis by implementing the Furthering the Blue Revolution Initiative (FABRI). This program helps create Middle East and North Africa Network of Water Centers of Excellence (MENA NWC). Designed and launched by USAID through FABRI, DAI has partnered with the UC Davis College of Agricultural and Environmental Sciences International Programs office to provide critical guidance on water resource and wastewater management in the formation of MENA NWC. The Center for Watershed Sciences is spearheading UC Davis participation in FABRI. UC Davis, along with four other U.S. public universities, is providing strategic guidance and research assistance to developing countries in these regions. It is the beginning of a long-term relationship with USAID and a continuation of the Center’s work in support of international research.
|Using 2-D Models for Flood Insurance Maps||
This project aims to improve the understanding and application of two-dimensional (2-D) models in producing flood insurance maps for California and the nation.
Communities covered by the National Flood Insurance Program and their consultants are gradually moving from 1-D models to 2-D models to better estimate flooding risks. The Federal Emergency Management Agency (FEMA), which administers the insurance program, has determined that technicians and decision-makers need more guidance on 2-D models in making accurate floodplain maps.
To provide that guidance, FEMA commissioned UC Davis to:
|Water Quality and Hydrodynamics||
Hydrodynamics and Water Quality in the Sacramento San Joaquin Delta
Sea level rise, large-scale flooding, and new conveyance arrangements for water exports may increase future water salinity for local agricultural production in California’s Sacramento-San Joaquin Delta. Increasing salinity in crop root zones often decreases crop yields and crop revenues. Salinity effects are nonlinear and vary with crop choice and other factors including drainage and residence time of irrigation water. Here, we explore changes in agricultural production in the Delta under various combinations of water management, large-scale flooding and future sea level rise. Water management alternatives include through-Delta water exports (current conditions), dual conveyance (through-Delta and a 6,700 Mm3yr-1 [or 7500 cfs] capacity peripheral canal or tunnel) and the flooding of five western islands with and without peripheral exports. We employ results from previous hydrodynamic simulations of likely changes in salinity for irrigation water at points in the Delta. We connect these irrigation water salinity values into a detailed agro-economic model of Delta agriculture to estimate local crop yield and farm revenue losses. Previous hydrodynamic modeling work shows that sea level rise is likely to increase salinity from 4% to 130% in this century, depending on the increase in sea level and location. Changes in water management under dual conveyance increase salinity mostly in the western Delta, and to a lesser extent in the north, where current salinity levels are now quite low. Because locations likely to experience the largest salinity increases already have a lower-value crop mix, the worst case losses are less than one percent of total Delta crop revenues. This result also holds for salinity increases from permanent flooding of western islands that serve as a salinity barrier. Our results suggest that salinity increases could have much smaller economic effects on Delta farming than other likely changes in the Delta such as retirement of agricultural lands following large-scale flooding and habitat development. Integrating hydrodynamic, water salinity, and economic models can provide insights into controversial management issues.
|Historical Delta Elevation Model||
Early 19th century settlers of the Sacramento-San Joaquin Delta would have a hard time recognizing the place today. Artificial levees for flood control, debris from hydraulic mining, deepwater shipping channels and massive water exports have fundamentally altered the region's landscapes, ecosystems and functions. Working with the San Francisco Estuary Institute and Research Management Associates of Fairfield, Center researchers developed a model of the early 1800s Delta to characterize the hydrodynamics under natural conditions.
Primary inputs to the bathymetric-topographic digital elevation model include two-dimensional Delta channels and land cover data from previous historical ecology mapping (Whipple et al. 2012); elevation data from historical US Coast Survey hydrographs and early river surveys.
We developed novel methods to interpolate between sparse historical soundings, infer depths of non-navigable channels from channel width, and convert historical tidal datums to modern fixed datums. The resulting 2-meter resolution digital elevation model covers Delta historical channels, tidal wetlands, adjacent non-tidal freshwater wetlands and upland transitional areas below 25 feet in elevation.
The small-scale farmers of the Dulcepamba watershed, located on the southwestern slopes of the Andes in central Ecuador, have provided fresh produce to local and domestic markets for generations. But these farmers were threatened first by allocation of water rights to Hidrotambo, the operator of a new hydroelectric facility in the basin, and next by fatal flooding that struck during hydroelectric construction.
Residents of the Dulcepamba watershed have resisted the hydroelectric project since it first received building permits in 2004, but with little success. Local farmers and other residents argued that the Hidrotambo water rights concession threatened the rights of the 72 small communities upstream of the hydroelectric facility. Against that background, a flood in March 2015 destroyed cropland, eight houses, and killed two women and a child in the village of San Pablo de Amalí.
A coalition of Dulcepamba residents and their supporters contacted researchers from the Center for Watershed Sciences (CWS) at the University of California, Davis and asked them to complete a forensic analysis of the March 2015 flood and model the hydrology of the watershed. The UC Davis researchers developed (1) a hydrologic model of Dulcepamba basin; and (2) a hydraulic model to assess hydraulic and geomorphic processes associated with the March 2015 flood.
The results produced by the hydrologic and hydraulic modeling completed here indicate that the March 2015 flood event on the Dulcepamba River would not have caused the damage that ultimately occurred in San
Pablo de Amalí but for other human activities at the site, in particular construction within the channel, diversion of flow, and obstruction by debris. The flow generated in the March 2015 flood was smaller than previous historical storms that did not cause the severe damage seen in 2015.
In addition, UC Davis hydrologic modeling of the Dulcepamba watershed showed that, when Hidrotambo’s use right was added to required environmental minimum flows, the total exceeded average daily flows nearly 70% of the time. In other words, the hydroelectric water allocation exceeded the total water available in the basin through most of the summer dry season, leaving nothing left for local farmers or residents.