John A. Dracup

Basin‐scale water system operations with uncertain future climate conditions: Methodology and case studies

[1]xa0The old and useful paradigm used by water resource engineers, that hydrology in a given place is stationary, and hence it is sufficient to look into the past to plan for the future, does not hold anymore, according to climate change projections. This becomes especially true in snow-dominated regions like California, where not only the magnitude but also the timing of streamflow could be affected by changes in precipitation and temperature. To plan and operate water resources systems at the basin scale, it is necessary to develop new tools that are suited for this nonstationary world. In this paper we develop an optimization algorithm that can be used for different studies related to climate change and water resources management. Three applications of this algorithm are developed for the Merced River basin. The first of these gives an assessment of the climate change effects on the operations of this basin considering an adaptive management strategy embedded in the optimization algorithm. In a second application we explore different long-term adaptation strategies intended to mitigate the effects of climate change. A final application is developed to determine how beneficial it is to build a new reservoir considering explicitly the uncertainty about future climate projections.

Model integration for assessing future hydroclimate impacts on water resources, agricultural production and environmental quality in the San Joaquin Basin, California

The US National Assessment of the Potential Consequences of Climate Variability and Change provides compelling arguments for action and adaptive measures to help mitigate water resource, agricultural production and environmental quality impacts of future climate change. National resource planning at this scale can benefit by the development of integrated impact analysis toolboxes that allow linkage and integration of hydroclimate models, surface and groundwater hydrologic models, economic and environmental impact models and techniques for social impact assessment. Simulation models used in an assessment of climate change impacts on water resources, agriculture and environmental quality in the San Joaquin Basin of California are described in this paper as well as the challenges faced in linking the component models within an impacts assessment toolbox. Results from simulations performed with several of the tools in the impacts assessment toolbox are presented and discussed. After initially attempting model integration with the public domain, GIS-based modeling framework Modular Modeling System/Object User Interface (MMS/OUI), frustration with the framework’s lack of flexibility to handle monthly timestep models prompted development of a common geodatabase to allow linkage of model input and output for the linked simulation models. A GIS-based data browser was also developed that works with both network flow models and makes calls to a model post-processor that shows model output for each selected node in each model network. This data and output browser system is flexible and can readily accommodate future changes in the model network configuration and in the model database. uf6d9 2003 Elsevier Ltd. All rights reserved.

COMPARISON OF TREE SPECIES SENSITIVITY TO HIGH AND LOW EXTREME HYDROCLIMATIC EVENTS

We present here a six-species comparison of tree-ring growth response to extremes (below the 30th and above the 70th percentile) in temperature, precipitation, and corresponding streamflow. The species compared are Pinus edulis (PIED), Pseudotsuga menziesii (PSME), Pinus ponderosa (PIPO), Pinus flexilis (PIFL), Pinus aristata (PIAR), and Picea engelmannii (PCEN). Sensitivity was determined using contingency scores obtained by comparing tree-ring growth at different lags with hydroclimatic observations from the Upper Colorado River Basin in the southwestern United States. The scores were computed using dual scaling methods in which the higher scores are assigned to stronger relationships between tree-ring growth and severe hydroclimatic occurrences. At lag 0, PIED and PSME present the greatest sensitivity to severe streamflow events. For precipitation and temperature the most sensitive species at lag 0 are PIED and PIPO. PIAR and PCEN show no significant relationship with extreme hydroclimatic events. PIFL shows more uniform lag-to-lag scores, suggesting a higher year-to-year persistence for this species. In general, tree-ring growth for all sensitive species is more responsive to hot-dry than to cool-moist extreme conditions. The scoring method proposed in this study for the analysis of tree-ring records proved to be a useful tool for evaluating ring-width sensitivity to extreme climatic forcing.

An integrated modeling system for environmental impact analysis of climate variability and extreme weather events in the San Joaquin Basin, California

Abstract This collaborative research project has two main objectives: to assess the vulnerability of water supply, water demand, water quality, ecosystem health and socioeconomic welfare within the San Joaquin River Basin as a function of climate variability and extreme weather events; and to provide guidance in the formulation of effective management strategies to mitigate the range of potential impacts due to climate variability and extreme weather. The project involves updating and advancing previous studies on climate change in California. Climate data are based on new Global Circulation Model output from the statistical downscaling that converts GCM climate forecasts into local weather forecasts. The project applies these climate data to perturb an existing 72-year historical hydrologic time series of the San Joaquin Basin to develop an integrated impacts analysis of climate change/variability on the water, economic and social resources of the Basin. Previous studies focused only on water resource impacts. A decision support system (DSS) is under development that will provide assistance to CALFED (a joint California State and Federal program designed to resolve water issues in the Bay–Delta) in water resource and ecosystem management of the San Joaquin Basin.

A hybrid system model of seasonal snowpack water balance

It is estimated that seasonal snow cover is the primary source of water supply for over 60 million people in the western United States. Informed decision making, which ensures reliable and equitable distribution of this limited water resource, thus needs to be motivated by an understanding of the physical snowmelt process. We present a direct application of hybrid systems for the modeling of the seasonal snowmelt cycle, and show that through the hybrid systems framework it is possible to significantly reduce the complexity offered by conventional PDE modeling methods. Our approach shows how currently existing heuristics can be embedded into a coherent mathematical framework to allow for powerful analytical techniques while preserving physical intuition about the problem. Snowmelt is modeled as a three state hybrid automaton, representing the sub-freezing, sub-saturated, and fully saturated physical states that an actual snowpack experiences. We show that the model accurately reproduces melt patterns, by simulating over actual data sets collected in the Sierra Nevada mountains. We further explore the possibility of merging this model with a currently existing wireless sensing infrastructure to create reliable prediction techniques that will feed into large scale control schemes of dams in mountain areas.

The 2009–2010 El Niño: Hydrologic Relief to U.S. Regions

Current forecasts by the U.S. National Oceanic and Atmospheric Administration (NOAA) are that the Pacific Ocean will experience El Nino conditions in late 2009 and into 2010. These forecasts are similar to past El Ni˜o events in 1972–1973, 1982–1983, 1986–1987, and 2002–2003. n nEvaluating the hydrologic conditions for these past El Nino events reveals that during these times, surface water supply conditions improved in many parts of the United States, including the Southeast, Midwest, and Southwest. At the same time, the Pacific Northwest and other specific regions of the United States experienced below-average water supply conditions. This is consistent with the long-established linkages between oceanic-atmospheric phenomena, El Nino, and streamflow [e.g., Kahya and Dracup, 1993; Tootle et al., 2005].

The Conjunctive Use of Reservoirs and Aquifers: Tradeoffs in Electricity Generation and Water Supply

Although the literature on conjunctive use of surface and groundwater is extensive few papers have analyzed the benefits of coordinating reservoir and aquifer operations. In this work we evaluate reservoir and aquifer operations under three different management schemes. We constructed a monthly non-linear programming model embedded into an annual stochastic dynamic programming model (SDP/NLP model). This model was applied to a case study of the operations of the Merced River Basin, located in the eastern San Joaquin Valley. In a first phase of this application we calibrate the model parameters to match historic operations and the historic level of reservoir-aquifer coordination. We then use the model to estimate the benefits of managing water storage under different institutional and economic scenarios. The scenarios include an electric power scenario (where the reservoir is operated to maximize hydropower benefits), a conjunctive use scenario (where reservoir and aquifer releases are jointed managed to maximize hydropower and agricultural benefits), and a non conjunctive use scenario (where the reservoir is operated independently of groundwater controls).