Richard N. Palmer

Projected impacts of climate change on salmon habitat restoration

Throughout the world, efforts are under way to restore watersheds, but restoration planning rarely accounts for future climate change. Using a series of linked models of climate, land cover, hydrology, and salmon population dynamics, we investigated the impacts of climate change on the effectiveness of proposed habitat restoration efforts designed to recover depleted Chinook salmon populations in a Pacific Northwest river basin. Model results indicate a large negative impact of climate change on freshwater salmon habitat. Habitat restoration and protection can help to mitigate these effects and may allow populations to increase in the face of climate change. The habitat deterioration associated with climate change will, however, make salmon recovery targets much more difficult to attain. Because the negative impacts of climate change in this basin are projected to be most pronounced in relatively pristine, high-elevation streams where little restoration is possible, climate change and habitat restoration together are likely to cause a spatial shift in salmon abundance. River basins that span the current snow line appear especially vulnerable to climate change, and salmon recovery plans that enhance lower-elevation habitats are likely to be more successful over the next 50 years than those that target the higher-elevation basins likely to experience the greatest snow–rain transition.

Water resources implications of global warming: a U.S. regional perspective.

The implications of global warming for the performance of six U.S. water resource systems are evaluated. The six case study sites represent a range of geographic and hydrologic, as well as institutional and social settings. Large, multi-reservoir systems (Columbia River, Missouri River, Apalachicola-Chatahoochee-Flint (ACF) Rivers), small, one or two reservoir systems (Tacoma and Boston) and medium size systems (Savannah River) are represented. The river basins range from mountainous to low relief and semi-humid to semi-arid, and the system operational purposes range from predominantly municipal to broadly multi-purpose. The studies inferred, using a chain of climate downscaling, hydrologic and water resources systems models, the sensitivity of six water resources systems to changes in precipitation, temperature and solar radiation. The climate change scenarios used in this study are based on results from transient climate change experiments performed with coupled ocean-atmosphere General Circulation Models (GCMs) for the 1995 Intergovernmental Panel on Climate Change (IPCC) assessment. An earlier doubled-CO2 scenario from one of the GCMs was also used in the evaluation. The GCM scenarios were transferred to the local level using a simple downscaling approach that scales local weather variables by fixed monthly ratios (for precipitation) and fixed monthly shifts (for temperature). For those river basins where snow plays an important role in the current climate hydrology (Tacoma, Columbia, Missouri and, to a lesser extent, Boston) changes in temperature result in important changes in seasonal streamflow hydrographs. In these systems, spring snowmelt peaks are reduced and winter flows increase, on average. Changes in precipitation are generally reflected in the annual total runoff volumes more than in the seasonal shape of the hydrographs. In the Savannah and ACF systems, where snow plays a minor hydrological role, changes in hydrological response are linked more directly to temperature and precipitation changes. Effects on system performance varied from system to system, from GCM to GCM, and for each system operating objective (such as hydropower production, municipal and industrial supply, flood control, recreation, navigation and instream flow protection). Effects were generally smaller for the transient scenarios than for the doubled CO2 scenario. In terms of streamflow, one of the transient scenarios tended to have increases at most sites, while another tended to have decreases at most sites. The third showed no general consistency over the six sites. Generally, the water resource system performance effects were determined by the hydrologic changes and the amount of buffering provided by the systems storage capacity. The effects of demand growth and other plausible future operational considerations were evaluated as well. For most sites, the effects of these non-climatic effects on future system performance would about equal or exceed the effects of climate change over system planning horizons.

Seasonal Residential Water Demand Forecasting for Census Tracts

The paucity of readily available demographic, economic, and water consumption data at household levels has limited the application of disaggregate water demand models. This research develops regression-based water demand models capable of forecasting single-family residential water demands within individual census tracts at a bimonthly time-step. The regression models are estimated using 12 years of demographic, weather, economic, and metered bimonthly water consumption data associated with over 100 unique census tracts in Seattle, Washington. In general, the three regression methods perform well in replicating total single-family water consumption in the study region. Two regression models, a fixed effects model and a random effects model, provide better estimates of water demand within individual census tracts. Improved water demand forecasts at the spatial scale of census tracts provide policy makers and planners information useful for managing water resources. These proposed approaches allow examinati...

Decision Support System for Optimizing Reservoir Operations Using Ensemble Streamflow Predictions

This paper investigates the value of ensemble streamflow predictions and energy price forecasts as aid to decision makers in scheduling the quantity and timing of reservoir releases for daily, weekly, and seasonal operations while meeting regulatory constraints. A decision support system DSS is described as it incorporates two integrated models of system operation: a simulation model that replicates general operating rules for the hydropower system and an optimization model that refines operations based upon forecasts of state variables. The DSS provides a series of recommendations for the quantity and timing of reservoir releases to optimize the economic value of the electrical energy produced, while balancing requirements and concerns related to flood control, environmental flows, and water supply. The DSS generates a range of optimal reservoir releases using an ensemble streamflow forecast and identifies robust operational solutions. The results indicate the value of the forecasts in improving system operation.

Modeling Water Resources Opportunities, Challenges and Trade-offs: The Use of Shared Vision Modeling for Negotiation and Conflict Resolution

1. Abstract This paper introduces the concept of Shared Vision Modeling and discusses its relevance to developing solutions to highly conflicted water resources problems. It begins by suggesting that although our computing resources have increased dramatically during the past two decades, our success rate in implementing computer generated solutions to water resources problems has not. The paper focuses on the use of Shared Vision modeling to guide model construction and to ensure that models are successfully integrated into the broader conflict resolution process. The paper concludes with examples of where Shared Vision Models have been used and summarizing their relative success.

Optimal Drought Management Using Sampling Stochastic Dynamic Programming with a Hedging Rule

This study develops procedures that calculate optimal water release curtailments during droughts using a future value function derived with a sampling stochastic dynamic programming model. Triggers that switch between a normal operating policy and an emergency operating policy (EOP) are based on initial reservoir storage values representing a 95% water supply reliability and an aggregate drought index that employs 6-month cumulative rainfall and 4-month cumulative streamflow. To verify the effectiveness of the method, a cross-validation scheme (using 2,100 combination sets) is employed to simulate the Geum River basin system in Korea. The simulation results demonstrate that the EOP approach: (1) reduces the maximum water shortage; (2) is most valuable when the initial storages of the drawdown period are low; and (3) is superior to other approaches when explicitly considering forecast uncertainty.

Reservoir management optimization for basin-wide ecological restoration in the Connecticut River.

AbstractEvidence from ecological studies suggests that the alteration of river flows downstream of reservoirs can threaten native aquatic ecosystems and the services they offer. Innovative revisions to water management practices are required to improve the health of aquatic species while maintaining the benefits from current infrastructure projects. The impacts of individual reservoir operations on ecosystem vitality are often masked by the uncoordinated and compounding influences of several impoundments upstream, undermining the examination of environmental impacts from particular reservoirs in a large watershed system. This paper presents a large-scale optimization model that investigates the value of coordinated reservoir management practices for ecological benefits in a large watershed with several major reservoir systems operating for a range of management objectives. An application of the model is presented for the Connecticut River watershed, the largest river basin in New England and one of the mo...

The Impacts of Climate Change on Portland's Water Supply: An Investigation of Potential Hydrologic and Management Impacts on the Bull Run System

Introduction The initial report of the Intergovernmental Panel on Climate Change (IPCC 1990) and those that have followed (IPCC 2001) conclude that our climate is changing. One of the most important impacts of climate change is on the worlds fresh water supplies, caused by increased temperatures, changed precipitation, and shifts in the historic hydrologic cycle. These changes are of particular interest in the Pacific Northwest because of the interplay between precipitation and temperature. Changes in temperature alter the delicate interactions between the amount of precipitation that falls as rain and snow, the accumulation of snow during the winter, and when this snow melts and contributes to streamflow. In addition, climate change can alter the demand for water, with demands increasing during dry, warm periods and decreasing during cool, wet periods. These changes in availability and demand of water will impact municipalities that are charged with providing safe and reliable drinking water. Climate change may impact a municipalitys ability to provide water to existing customers and their planning for the future. New sources of water may be required, and the evaluation of these new sources should consider potential climate change. This study explores the impact that climate change will have on the Bull Run watershed and the Portland Water Bureaus (PWB) ability to provide reliable water to its customers. The study uses a series of linked models to address the potential impacts of climate change. These models simulate three aspects of the process: the climate, the hydrologic cycle, and water supply system management. The results of this study are of particular relevance, as the PWB has recently completed a comprehensive water plan and must now decide which of several potential alternatives it should pursue in continuing to provide safe and reliable water. Currently, water demands are met with two major dams in the Bull Run watershed and with groundwater. The active capacities of the dams are small (10.2 billion gallons) relative to the flows delivered from their watersheds, thus they refill annually. A number of system expansion alternatives are being considered, including the construction of Dam 3 in the Bull Run basin and the expanded use of groundwater. Dam 3 would double the available surface storage in the basin whereas expansion of the groundwater sources will make the PWB more dependent on subsurface sources. Growing regional water demands will compromise PWBs current ability to provide water reliably during drought events in …

Computer Assisted Decision Support System for High Level Infrastructure Master Planning: Case of the City of Portland Supply and Transmission Model (STM)

Quantitative techniques and computer-based models were first introduced into the water resources discipline in the early 1960s. Since then models developed for and applied to various aspects of managing water resources have evolved from black box paradigms to complex and comprehensive user-friendly interactive computer models. These efforts have been motivated by the apparent and increasing demand for more effective planning and policy making, and to aid in operating complex and often multi-objective and multi-purpose water resources systems. The success and effectiveness of water resources computer models in public agencies is impacted by the institutional framework in which the model was developed, the existence of an effective interface mechanism that can link modeler-model-user interactions, and the models contribution to facilitate and support the decision making process. The Supply and Transmission Model (STM) was developed to support a large infrastructure master plan designed to explore a wide variety of water supply, water management and water transmission options for the Portland Water Bureau (PWB). The model is a highly interactive evaluation tool, allowing PWB staff to create a shared understanding of the models assumptions and encourage the Water Bureau staff to explore how various future expansion and conservation alternatives will allow them to meet their water supply and natural resources management goals. The model has been created in the STELLA Research 5.1.1 simulation environment. One of the purposes of this paper is to discuss the critical factors that have contributed to the acceptance of STM as a planning decision support tool for the PWB.

Subjective evaluation: linguistic scales in pairwise comparison methods

Abstract This technical note reviews the application of a simple pairwise comparison method to multi-objective subjective evaluation problems and reports the results of an experiment exploring the use of linguistic scales in soliciting responses for Saatys pairwise comparison method. The experimental results also illustrate the usefulness of a subjective evaluation technique in structural engineering.