Precipitation extremes and changes in snowmelt response that drive flood events affect many decis... more Precipitation extremes and changes in snowmelt response that drive flood events affect many decisions with respect to infrastructure including dam and levee safety and flood plain delineation. In light of the current understanding of the potential effects of climate change on precipitation events the emphasis on exploring future changes on floods is expanding. In previous work it has been shown
Erosion prediction tools are essential for many different aspects of land management. In this pap... more Erosion prediction tools are essential for many different aspects of land management. In this paper we examine the applicability of scaling relationships developed for river networks for the description of hillslope erosion channel networks. Eight erosion channel networks were studied on mine spoil sites in Kemmerer, Wyoming. We analysed these networks using well-known geomorphological relationships such as Horton's laws and Melton's law. An analysis of the erosion channel hydraulic geometry described by a series of power functions was also conducted. We found that the network geometry resembles larger river networks, and that the cross-sectional shapes of individual erosion channels exhibit statistical characteristics of their larger river counterparts.
tained. Note in the original manuscript on page 2016, line 27 denotes that “The general approach ... more tained. Note in the original manuscript on page 2016, line 27 denotes that “The general approach was to scale a monthly set of observed daily values . . .” This more accurately should say to scale a monthly set of observed six-hourly values. This paragraph goes on to describe this process in detail with a example onto page 2017. Therefore to alleviate some of reviewer Sivapalan’s concerns any intermittency that has been observed in the data set is maintained through the temporal downscaling methodology.
Storage and controlled distribution of water have been key elements of a human strategy to overco... more Storage and controlled distribution of water have been key elements of a human strategy to overcome the space and time variability of water, which have been marked by catastrophic droughts and floods throughout the course of civilization. In the United States, the peak of dam building occurred in the mid-20th century with knowledge limited to the scientific understanding and hydrologic records of the time. Ecological impacts were considered differently than current legislative and regulatory controls would potentially dictate. Additionally, future costs such as maintenance or removal beyond the economic design life were not fully considered. The converging risks associated with aging water storage infrastructure and uncertainty in climate in addition to the continuing need for water storage, flood protection, and hydropower result in a pressing need to address the state of dam infrastructure across the nation. Decisions regarding the future of dams in the United States may, in turn, influence regional water futures through groundwater outcomes, economic productivity, migration, and urban growth. We advocate for a comprehensive national water assessment and a formal analysis of the role dams play in our water future. We emphasize the urgent need for environmentally and economically sound strategies to integrate surface and groundwater storage infrastructure in local, regional, and national water planning considerations. A research agenda is proposed to assess dam failure impacts and the design, operation, and need for dams considering both paleo and future climate, utilization of groundwater resources, and the changing societal values toward the environment. Plain Language Summary Water storage and control have been key elements of a human strategy to overcome differences between water availability and water needs. The future promises changes to when and where water will be available and many regions in the USA will likely see an increase in the imbalance between existing water storage and evolving demands for water. This indicates the need for more storage or new dams to meet human and ecological needs. The current trend for removal of old, hazardous or unpopular dams now and into the future may impact regional groundwater outcomes, food and energy production, migration, and urban growth. We advocate for a formal analysis of the role dams play in the future of the USA's water landscape. We also stress the need for national water planning considerations to develop environmentally and economically sound strategies to integrate the management of surface and groundwater storage infrastructure in the USA.
NATO Science for Peace and Security Series C: Environmental Security, 2011
ABSTRACT The magnitude of climate change impacts facing water resources managers in the United St... more ABSTRACT The magnitude of climate change impacts facing water resources managers in the United States has spurred closer interagency cooperation in developing methods supporting planning and engineering for climate change adaptation. The two largest water resources management agencies in the U.S., the U.S. Army Corps of Engineers and the Bureau of Reclamation, have partnered to describe climate change challenges, identify user needs for improving tools and information, and assess capabilities to use weather and climate forecasts in federal water resources management. They have also hosted a forum with national and international experts exploring the issue of nonstationary hydrology with respect to climate change. In progress is development of multiagency guidelines for best practices to select from the portfolio of climate information including global climate scenarios, through general circulation models, through downscaling, to regional or watershed-scale hydrological and operations planning models to account properly for climate change and variability at the scale of water-resource operational decisions. This presentation describes collaborative activities and the resulting methods being used as both agencies plan for and implement climate change adaptation measures.
ABSTRACT Observed precipitation variability measures are compared to measures obtained using the ... more ABSTRACT Observed precipitation variability measures are compared to measures obtained using the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project (CMIP3) General Circulation Models (GCM) data from 36 model projections downscaled by Brekke at al. (2007) and 30 model projections downscaled by Jon Eischeid. Three groups of variability measures are considered in this historical period (1951-1999) comparison: a) basic variability measures, such as standard deviation, interdecadal standard deviation; b) exceedance probability values, i.e., 10% (extreme wet years) and 90% (extreme dry years) exceedance probability values of series of n-year running mean annual amounts, where n=1,12; 10% exceedance probability values of annual maximum monthly precipitation (extreme wet months); and c) runs variability measures, e.g., frequency of negative and positive runs of annual precipitation amounts, total number of the negative and positive runs. Two gridded precipitation data sets produced from observations are used: the Maurer et al. (2002) and the Daly et al. (1994) Precipitation Regression on Independent Slopes Method (PRISM) data sets. The data consist of monthly grid-point precipitation averaged on a United States Geological Survey (USGS) hydrological sub-region scale. The statistical significance of the obtained model minus observed measure differences is assessed using a block bootstrapping approach. The analyses were performed on annual, seasonal and monthly scale. The results indicate that the interdecadal standard deviation is underestimated, in general, on all time scales by the downscaled model data. The differences are statistically significant at a 0.05 significance level for several Lower Colorado Basin sub-regions on annual and seasonal scale, and for several sub-regions located mostly in the Upper Colorado River Basin for the months of March, June, July and November. Although the models simulate drier extreme wet years, wetter extreme dry years and drier extreme wet months for the Upper Colorado basin, the differences are mostly not-significant. Exceptions are the results about the extreme wet years for n=3 for sub-region White-Yampa, for n=6, 7, and 8 for sub-region Upper Colorado-Dolores, and about the extreme dry years for n=11 for sub-region Great Divide-Upper Green. None of the results for the sub-regions in the Lower Colorado Basin were significant. For most of the Upper Colorado sub-regions the models simulate significantly lower frequency of negative and positive 4-6 year runs, while for several sub-regions a significantly higher frequency of 2-year negative runs is evident in the model versus the Maurer data comparisons. The model projections versus the PRISM data comparison reveals similar results for the negative runs, while for the positive runs the results indicate that the models simulate higher frequency of the 2-6 year runs. The results for the Lower Colorado basin sub-regions are similar, in general, to these for the Upper Colorado sub-regions. The differences between the simulated and the observed total number of negative or positive runs were not significant for almost all of the sub-regions within the Colorado River Basin.
The Reclamation Dam Safety Program is charged with evaluating risk at over 400 dams in the Wester... more The Reclamation Dam Safety Program is charged with evaluating risk at over 400 dams in the Western United States. Current federal guidelines of flood estimations are based on the paradigm that a longer record of flood events produces a better estimate for future flood probability. This is the expanding retrospective paradigm that each additional year of flood information is used
Flood safety is of the utmost concern for water resources management agencies charged with operat... more Flood safety is of the utmost concern for water resources management agencies charged with operating and maintaining reservoir systems. Risk evaluations guide design of infrastructure alterations or lead to potential changes in operations. Changes in climate may change the risk due to floods and therefore decisions to alter infrastructure with a life span of decades or longer may benefit from
The SECURE Water Act § 9503(b)(2) authorizes the U.S. Department of Interior's Bureau of Recl... more The SECURE Water Act § 9503(b)(2) authorizes the U.S. Department of Interior's Bureau of Reclamation to assess climate change risks for water and environmental resources in eight "major Reclamation river basins" in the Western United States (i.e. Colorado, Columbia, Klamath, Missouri, Rio Grande, Sacramento, San Joaquin, and Truckee basins). The legislation calls for Reclamation to provide periodic reports on implications
Grazing can alter the spatial heterogeneity of vegetation, influencing ecosystem processes and bi... more Grazing can alter the spatial heterogeneity of vegetation, influencing ecosystem processes and biodiversity. Our objective was to identify why grazing causes increases in the spatial heterogeneity of vegetation in some cases, but decreases in others. The immediate effect of grazing on heterogeneity depends on the interaction between the spatial pattern of grazing and the preexisting spatial pattern of vegetation. Depending on the scale of observation and on the factors that determine animal distribution, grazing patterns may be stronger or weaker than vegetation patterns, or may mirror the spatial structure of vegetation. For each possible interaction between these patterns, we make a prediction about resulting changes in the spatial heterogeneity of vegetation. Case studies from the literature support our predictions, although ecosystems characterized by strong plantsoil interactions present important exceptions. While the processes by which grazing causes increases in heterogeneity are clear, how grazing leads to decreases in heterogeneity is less so. To explore how grazing can consistently dampen the fine-scale spatial patterns of competing plant species, we built a cell-based simulation model that features two competing plant species, different grazing patterns, and different sources of vegetation pattern. Only the simulations that included neighborhood interactions as a source of vegetation pattern produced results consistent with the predictions we derived from the literature review.
Flood safety is of the utmost concern for water resources management agencies charged with operat... more Flood safety is of the utmost concern for water resources management agencies charged with operating and maintaining reservoir systems. Risk evaluations guide design of infrastructure alterations or lead to potential changes in operations. Changes in climate may change the risk due to floods and therefore decisions to alter infrastructure with a life span of decades or longer may benefit from the use of climate projections as opposed to use of only historical observations. This manuscript presents a set of methods meant to support flood frequency evaluation based on current downscaled climate projections and the potential implications of changing flood risk on how evaluations are made. Methods are demonstrated in four case study basins: the Boise River above Lucky Peak Dam, the San Joaquin River above Friant Dam, the James River above Jamestown Dam, and the Gunnison River above Blue Mesa Dam. The analytical design includes three core elements: (1) a rationale for selecting climate projections to represent available climate projections; (2) generation of runoff projections consistent with climate projections using a process-based hydrologic model and temporal disaggregation of monthly downscaled climate projections into 6-h weather forcings required by the hydrologic model; and (3) analysis of flood frequency distributions based on runoff projection results. In addition to demonstrating the methodology, this paper also presents method choices under each analytical element, and the resulting implications to how flood frequencies are evaluated. The methods used reproduce the antecedent calibration period well. The approach results in a unidirectional shift in modeled flood magnitudes. The comparison between an expanding retrospective (current Correspondence to: D. A. Raff ([email protected]) paradigm for flood frequency estimation) and a lookahead flood frequency approach indicate potential for significant biases in flood frequency estimation.
Erosion prediction tools are essential for many different aspects of land management. In this pap... more Erosion prediction tools are essential for many different aspects of land management. In this paper we examine the applicability of scaling relationships developed for river networks for the description of hillslope erosion channel networks. Eight erosion channel networks were studied on mine spoil sites in Kemmerer, Wyoming. We analysed these networks using well-known geomorphological relationships such as Horton's laws and Melton's law. An analysis of the erosion channel hydraulic geometry described by a series of power functions was also conducted. We found that the network geometry resembles larger river networks, and that the cross-sectional shapes of individual erosion channels exhibit statistical characteristics of their larger river counterparts.
Precipitation extremes and changes in snowmelt response that drive flood events affect many decis... more Precipitation extremes and changes in snowmelt response that drive flood events affect many decisions with respect to infrastructure including dam and levee safety and flood plain delineation. In light of the current understanding of the potential effects of climate change on precipitation events the emphasis on exploring future changes on floods is expanding. In previous work it has been shown
Erosion prediction tools are essential for many different aspects of land management. In this pap... more Erosion prediction tools are essential for many different aspects of land management. In this paper we examine the applicability of scaling relationships developed for river networks for the description of hillslope erosion channel networks. Eight erosion channel networks were studied on mine spoil sites in Kemmerer, Wyoming. We analysed these networks using well-known geomorphological relationships such as Horton's laws and Melton's law. An analysis of the erosion channel hydraulic geometry described by a series of power functions was also conducted. We found that the network geometry resembles larger river networks, and that the cross-sectional shapes of individual erosion channels exhibit statistical characteristics of their larger river counterparts.
tained. Note in the original manuscript on page 2016, line 27 denotes that “The general approach ... more tained. Note in the original manuscript on page 2016, line 27 denotes that “The general approach was to scale a monthly set of observed daily values . . .” This more accurately should say to scale a monthly set of observed six-hourly values. This paragraph goes on to describe this process in detail with a example onto page 2017. Therefore to alleviate some of reviewer Sivapalan’s concerns any intermittency that has been observed in the data set is maintained through the temporal downscaling methodology.
Storage and controlled distribution of water have been key elements of a human strategy to overco... more Storage and controlled distribution of water have been key elements of a human strategy to overcome the space and time variability of water, which have been marked by catastrophic droughts and floods throughout the course of civilization. In the United States, the peak of dam building occurred in the mid-20th century with knowledge limited to the scientific understanding and hydrologic records of the time. Ecological impacts were considered differently than current legislative and regulatory controls would potentially dictate. Additionally, future costs such as maintenance or removal beyond the economic design life were not fully considered. The converging risks associated with aging water storage infrastructure and uncertainty in climate in addition to the continuing need for water storage, flood protection, and hydropower result in a pressing need to address the state of dam infrastructure across the nation. Decisions regarding the future of dams in the United States may, in turn, influence regional water futures through groundwater outcomes, economic productivity, migration, and urban growth. We advocate for a comprehensive national water assessment and a formal analysis of the role dams play in our water future. We emphasize the urgent need for environmentally and economically sound strategies to integrate surface and groundwater storage infrastructure in local, regional, and national water planning considerations. A research agenda is proposed to assess dam failure impacts and the design, operation, and need for dams considering both paleo and future climate, utilization of groundwater resources, and the changing societal values toward the environment. Plain Language Summary Water storage and control have been key elements of a human strategy to overcome differences between water availability and water needs. The future promises changes to when and where water will be available and many regions in the USA will likely see an increase in the imbalance between existing water storage and evolving demands for water. This indicates the need for more storage or new dams to meet human and ecological needs. The current trend for removal of old, hazardous or unpopular dams now and into the future may impact regional groundwater outcomes, food and energy production, migration, and urban growth. We advocate for a formal analysis of the role dams play in the future of the USA's water landscape. We also stress the need for national water planning considerations to develop environmentally and economically sound strategies to integrate the management of surface and groundwater storage infrastructure in the USA.
NATO Science for Peace and Security Series C: Environmental Security, 2011
ABSTRACT The magnitude of climate change impacts facing water resources managers in the United St... more ABSTRACT The magnitude of climate change impacts facing water resources managers in the United States has spurred closer interagency cooperation in developing methods supporting planning and engineering for climate change adaptation. The two largest water resources management agencies in the U.S., the U.S. Army Corps of Engineers and the Bureau of Reclamation, have partnered to describe climate change challenges, identify user needs for improving tools and information, and assess capabilities to use weather and climate forecasts in federal water resources management. They have also hosted a forum with national and international experts exploring the issue of nonstationary hydrology with respect to climate change. In progress is development of multiagency guidelines for best practices to select from the portfolio of climate information including global climate scenarios, through general circulation models, through downscaling, to regional or watershed-scale hydrological and operations planning models to account properly for climate change and variability at the scale of water-resource operational decisions. This presentation describes collaborative activities and the resulting methods being used as both agencies plan for and implement climate change adaptation measures.
ABSTRACT Observed precipitation variability measures are compared to measures obtained using the ... more ABSTRACT Observed precipitation variability measures are compared to measures obtained using the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project (CMIP3) General Circulation Models (GCM) data from 36 model projections downscaled by Brekke at al. (2007) and 30 model projections downscaled by Jon Eischeid. Three groups of variability measures are considered in this historical period (1951-1999) comparison: a) basic variability measures, such as standard deviation, interdecadal standard deviation; b) exceedance probability values, i.e., 10% (extreme wet years) and 90% (extreme dry years) exceedance probability values of series of n-year running mean annual amounts, where n=1,12; 10% exceedance probability values of annual maximum monthly precipitation (extreme wet months); and c) runs variability measures, e.g., frequency of negative and positive runs of annual precipitation amounts, total number of the negative and positive runs. Two gridded precipitation data sets produced from observations are used: the Maurer et al. (2002) and the Daly et al. (1994) Precipitation Regression on Independent Slopes Method (PRISM) data sets. The data consist of monthly grid-point precipitation averaged on a United States Geological Survey (USGS) hydrological sub-region scale. The statistical significance of the obtained model minus observed measure differences is assessed using a block bootstrapping approach. The analyses were performed on annual, seasonal and monthly scale. The results indicate that the interdecadal standard deviation is underestimated, in general, on all time scales by the downscaled model data. The differences are statistically significant at a 0.05 significance level for several Lower Colorado Basin sub-regions on annual and seasonal scale, and for several sub-regions located mostly in the Upper Colorado River Basin for the months of March, June, July and November. Although the models simulate drier extreme wet years, wetter extreme dry years and drier extreme wet months for the Upper Colorado basin, the differences are mostly not-significant. Exceptions are the results about the extreme wet years for n=3 for sub-region White-Yampa, for n=6, 7, and 8 for sub-region Upper Colorado-Dolores, and about the extreme dry years for n=11 for sub-region Great Divide-Upper Green. None of the results for the sub-regions in the Lower Colorado Basin were significant. For most of the Upper Colorado sub-regions the models simulate significantly lower frequency of negative and positive 4-6 year runs, while for several sub-regions a significantly higher frequency of 2-year negative runs is evident in the model versus the Maurer data comparisons. The model projections versus the PRISM data comparison reveals similar results for the negative runs, while for the positive runs the results indicate that the models simulate higher frequency of the 2-6 year runs. The results for the Lower Colorado basin sub-regions are similar, in general, to these for the Upper Colorado sub-regions. The differences between the simulated and the observed total number of negative or positive runs were not significant for almost all of the sub-regions within the Colorado River Basin.
The Reclamation Dam Safety Program is charged with evaluating risk at over 400 dams in the Wester... more The Reclamation Dam Safety Program is charged with evaluating risk at over 400 dams in the Western United States. Current federal guidelines of flood estimations are based on the paradigm that a longer record of flood events produces a better estimate for future flood probability. This is the expanding retrospective paradigm that each additional year of flood information is used
Flood safety is of the utmost concern for water resources management agencies charged with operat... more Flood safety is of the utmost concern for water resources management agencies charged with operating and maintaining reservoir systems. Risk evaluations guide design of infrastructure alterations or lead to potential changes in operations. Changes in climate may change the risk due to floods and therefore decisions to alter infrastructure with a life span of decades or longer may benefit from
The SECURE Water Act § 9503(b)(2) authorizes the U.S. Department of Interior's Bureau of Recl... more The SECURE Water Act § 9503(b)(2) authorizes the U.S. Department of Interior's Bureau of Reclamation to assess climate change risks for water and environmental resources in eight "major Reclamation river basins" in the Western United States (i.e. Colorado, Columbia, Klamath, Missouri, Rio Grande, Sacramento, San Joaquin, and Truckee basins). The legislation calls for Reclamation to provide periodic reports on implications
Grazing can alter the spatial heterogeneity of vegetation, influencing ecosystem processes and bi... more Grazing can alter the spatial heterogeneity of vegetation, influencing ecosystem processes and biodiversity. Our objective was to identify why grazing causes increases in the spatial heterogeneity of vegetation in some cases, but decreases in others. The immediate effect of grazing on heterogeneity depends on the interaction between the spatial pattern of grazing and the preexisting spatial pattern of vegetation. Depending on the scale of observation and on the factors that determine animal distribution, grazing patterns may be stronger or weaker than vegetation patterns, or may mirror the spatial structure of vegetation. For each possible interaction between these patterns, we make a prediction about resulting changes in the spatial heterogeneity of vegetation. Case studies from the literature support our predictions, although ecosystems characterized by strong plantsoil interactions present important exceptions. While the processes by which grazing causes increases in heterogeneity are clear, how grazing leads to decreases in heterogeneity is less so. To explore how grazing can consistently dampen the fine-scale spatial patterns of competing plant species, we built a cell-based simulation model that features two competing plant species, different grazing patterns, and different sources of vegetation pattern. Only the simulations that included neighborhood interactions as a source of vegetation pattern produced results consistent with the predictions we derived from the literature review.
Flood safety is of the utmost concern for water resources management agencies charged with operat... more Flood safety is of the utmost concern for water resources management agencies charged with operating and maintaining reservoir systems. Risk evaluations guide design of infrastructure alterations or lead to potential changes in operations. Changes in climate may change the risk due to floods and therefore decisions to alter infrastructure with a life span of decades or longer may benefit from the use of climate projections as opposed to use of only historical observations. This manuscript presents a set of methods meant to support flood frequency evaluation based on current downscaled climate projections and the potential implications of changing flood risk on how evaluations are made. Methods are demonstrated in four case study basins: the Boise River above Lucky Peak Dam, the San Joaquin River above Friant Dam, the James River above Jamestown Dam, and the Gunnison River above Blue Mesa Dam. The analytical design includes three core elements: (1) a rationale for selecting climate projections to represent available climate projections; (2) generation of runoff projections consistent with climate projections using a process-based hydrologic model and temporal disaggregation of monthly downscaled climate projections into 6-h weather forcings required by the hydrologic model; and (3) analysis of flood frequency distributions based on runoff projection results. In addition to demonstrating the methodology, this paper also presents method choices under each analytical element, and the resulting implications to how flood frequencies are evaluated. The methods used reproduce the antecedent calibration period well. The approach results in a unidirectional shift in modeled flood magnitudes. The comparison between an expanding retrospective (current Correspondence to: D. A. Raff ([email protected]) paradigm for flood frequency estimation) and a lookahead flood frequency approach indicate potential for significant biases in flood frequency estimation.
Erosion prediction tools are essential for many different aspects of land management. In this pap... more Erosion prediction tools are essential for many different aspects of land management. In this paper we examine the applicability of scaling relationships developed for river networks for the description of hillslope erosion channel networks. Eight erosion channel networks were studied on mine spoil sites in Kemmerer, Wyoming. We analysed these networks using well-known geomorphological relationships such as Horton's laws and Melton's law. An analysis of the erosion channel hydraulic geometry described by a series of power functions was also conducted. We found that the network geometry resembles larger river networks, and that the cross-sectional shapes of individual erosion channels exhibit statistical characteristics of their larger river counterparts.
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Papers by D. Raff