David E. Rheinheimer

Freshwater conservation options for a changing climate in California's Sierra Nevada

Catchments of Californias Sierra Nevada have been managed for hydropower, water supply, recreation and the environment, during which regional freshwater ecosystems have experienced extirpations of anadromous fishes, widespread loss in amphibian abundance and increases in non-native species. Californias Mediterranean-montane climateis expectedtowarmby 2-68C overthe nextcentury, reducingsnowpack,causingearlier runoffandalteringflows. Freshwater conservation efforts currently rely on a patchwork of legal and regulatory mechanisms, and have failed to achieve their full potential because of weak and uncoordinated implementation. No scheme adequately addresses freshwater conservation objectives such as representation and persistence, and all ignore anticipated impacts of climate change. We recommend that (1) existing legislation be fully implemented, with explicit anticipation of future conditions, (2) local institutions develop and implement a systematic freshwater conservation plan, focusing on resilience to climate warming, (3) policies be crafted to prioritise catchments to emphasise key regional objectives (e.g. conservation) and (4) regional planning agencies with regulatory authority be formed at the catchment level.

Optimizing Selective Withdrawal from Reservoirs to Manage Downstream Temperatures with Climate Warming

AbstractSelective withdrawal systems can take advantage of thermal stratification in reservoirs to manage downstream temperatures. Selective withdrawal might also help adapt operations to environmental changes, such as increased stream temperatures expected with climate change. This exploratory study develops a linear programming model to release water from different thermal pools in reservoirs to minimize deviations from target downstream temperatures. The model is applied with representative thermal dynamics to Lake Spaulding, a multipurpose reservoir on the South Fork Yuba River in California with climate warming represented by uniform increases in air temperature. Optimization results for thermal pool management with selective withdrawal are compared to a single, low-level outlet release model. Optimal selective withdrawal hedges the winter release of cold water to decrease summer stream temperatures. With climate warming, selective withdrawal can help lessen stream warming in the summer but at a cost...

Application of Harmony Search Algorithm to Reservoir Operation Optimization

In this study, a meta-heuristic technique called harmony search (HS) algorithm is developed for reservoir operation optimization with respect to flood control. The HS algorithm is used to minimize the water supply deficit and flood damages downstream of a reservoir. The GIS database is used to determine the flood damage functions. The efficacy of HS algorithm is evaluated in comparison with other techniques by using a benchmark problem for a single reservoir operation optimization problem. HS showed promising results in terms of speed of convergence to an optimal objective function value compared with other techniques such as honey-bee mating optimization (HBMO) and a global optimization model (LINGO 8.0 NLP solver). The HS algorithm is then applied to the Narmab reservoir, north of Iran, as a case study. Narmab reservoir serves multiple purposes including irrigation, flood control, and drinking water requirements. The developed model is applied for monthly operation. The results show that the HS algorithm can be effectively used for operation of reservoir for flood management.

Identifying Explicit Formulation of Operating Rules for Multi-Reservoir Systems Using Genetic Programming

Operating rules have been widely used to handle the inflows uncertainty for reservoir long-term operations. Such rules are often expressed in implicit formulations not easily used by other operators and/or reservoirs directly. This study presented genetic programming (GP) to derive the explicit nonlinear formulation of operating rules for multi-reservoir systems. Steps in the proposed method include: (1) determining the optimal operation trajectory of the multi-reservoir system using the dynamic programming to solve a deterministic long-term operation model, (2) selecting the input variables of operating rules using GP based on the optimal operation trajectory, (3) identifying the formulation of operating rules using GP again to fit the optimal operation trajectory, (4) refining the key parameters of operating rules using the parameterization-simulation-optimization method. The method was applied to multi-reservoir system in China that includes the Three Gorges cascade hydropower reservoirs (Three Gorges and Gezhouba reservoirs) and the Qing River cascade hydropower reservoirs (Shuibuya, Geheyan and Gaobazhou reservoirs). The inflow and storage energy terms were selected as input variables for total output of the aggregated reservoir and for decomposition. It was shown that power energy term could more effectively reflect the operating rules than water quantity for the hydropower systems; the derived operating rules were easier to implement for practical use and more efficient and reliable than the conventional operating rule curves and artificial neural network (ANN) rules, increasing both average annual hydropower generation and generation assurance rate, indicating that the proposed GP formulation had potential for improving the operating rules of multi-reservoir system.

Simulating High-Elevation Hydropower with Regional Climate Warming in the West Slope, Sierra Nevada

Water systems in snowmelt-dominated hydroregions such as Californias Sierra Nevada mountains are sensitive to regional climate change, hydropower systems in particular. In this study, a water resources management model was developed for the upper west slope Sierra Nevada to understand the potential effects of regional climate warming on hydropower at the watershed scale, a scale that has been largely neglected but is important for hydroregional planning. The model is developed with the Water Evaluation and Planning system (WEAP) and includes most water management infrastructure in the study region. Hydropower is simulated assuming historical long-term electricity demand and a spill minimization rule. The method is suitable for simulating generation for most of the main watersheds in the region. To assess the potential effect of climate warming, uniform air temperature increases of 0°C, 2°C, 4°C, and 6°C were considered, with no change in precipitation, to approximate regional warming through 2100. The highly productive northern Sierra Nevada sees large re- ductions in hydropower generation with decreases in annual runoff. The central watersheds see less reduction in annual runoff and can adapt better to changes in runoff timing. Generation in southern watersheds, which are less productive, decreases. Results from this study can help identify which watersheds might easily adapt to climate change, where hydropower is likely to conflict with other uses, and where more detailed operational studies are needed. DOI: 10.1061/(ASCE)WR.1943-5452.0000373.

Climate-Adaptive Water Year Typing for Instream Flow Requirements in California’s Sierra Nevada

AbstractWater year types (WYTs), whereby years are classified by river runoff quantity compared to historical runoff, are one tool to help make major water management decisions. Increasingly, these decisions include instream flow requirements (IFRs) below dams for river ecosystem management. However, WYTs are typically based on assumptions of stationarity, and are thus rendered less meaningful with climate change. Hydrologic alteration resulting from climate change means that a WYT-based IFR scheme using stationary historical observations might inadvertently result in long-term river management outcomes inconsistent with original water management goals. This study assesses the management implications of assuming hydrologic nonstationarity in a WYT-based IFR scheme in California’s upper Yuba River and demonstrates a rolling period of record as a climate adaptation strategy. The existing, nonadaptive water management scheme leads to vastly different possible water allocation outcomes than originally planned...

Valuing year‐to‐go hydrologic forecast improvements for a peaking hydropower system in the Sierra Nevada

Author(s): Rheinheimer, DE; Bales, RC; Oroza, CA; Lund, JR; Viers, JH | Abstract: