The Experts below are selected from a list of 15927 Experts worldwide ranked by ideXlab platform
Dennis P Lettenmaier - One of the best experts on this subject based on the ideXlab platform.
-
seasonal hydrologic responses to climate change in the pacific northwest
Water Resources Research, 2015Co-Authors: Julie A Vano, Bart Nijssen, Dennis P LettenmaierAbstract:increased temperatures and Changes in Precipitation will result in fundamental Changes in the seasonal distribution of streamflow in the Pacific Northwest and will have serious implications for water resources management. To better understand local impacts of regional climate change, we conducted model experiments to determine hydrologic sensitivities of annual, seasonal, and monthly runoff to imposed annual and seasonal Changes in Precipitation and temperature. We used the Variable infiltration Capacity (VIC) land-surface hydrology model applied at 1/16° latitude-longitude spatial resolution over the Pacific Northwest (PNW), a scale sufficient to support analyses at the hydrologic unit code eight (HUC-8) basin level. These experiments resolve the spatial character of the sensitivity of future water supply to Precipitation and temperature Changes by identifying the seasons and locations where climate change will have the biggest impact on runoff. The PNW exhibited a diversity of responses, where transitional (intermediate elevation) watersheds experience the greatest seasonal shifts in runoff in response to cool season warming. We also developed a methodology that uses these hydrologic sensitivities as basin-specific transfer functions to estimate future Changes in long-term mean monthly hydrographs directly from climate model output of Precipitation and temperature. When principles of linearity and superposition apply, these transfer functions can provide feasible first-order estimates of the likely nature of future seasonal streamflow change without performing downscaling and detailed model simulations.
-
hydrologic sensitivities of colorado river runoff to Changes in Precipitation and temperature
Journal of Hydrometeorology, 2012Co-Authors: Julie A Vano, Dennis P LettenmaierAbstract:The Colorado River is the primary water source for much of the rapidly growing southwestern United States. Recent studies have projected reductions in Colorado River flows from less than 10% to almost 50% by midcentury because of climate change—a range that has clouded potential management responses. These differences in projections are attributable to variations in climate model projections but also to differing land surface model (LSM) sensitivities. This second contribution to uncertainty—specifically, variations in LSM runoff change with respect to Precipitation (elasticities) and temperature (sensitivities)—are evaluated here through comparisons of multidecadal simulations from five commonly used LSMs (Catchment, Community Land Model, Noah, Sacramento Soil Moisture Accounting model, and Variable infiltration Capacity model) all applied over the Colorado River basin at 1/88 latitude by longitude spatial resolution. The annual elasticity of modeled runoff (fractional change in annual runoff divided by fractional change in annual Precipitation) at Lees Ferry ranges from two to six for the different LSMs. Elasticities generally are higher in lower Precipitationand/orrunoffregimes;hence,the highestvaluesare formodelsbiasedlow in runoffproduction,and the range of elasticities is reduced to two to three when adjusted to current runoff climatology. Annual temperature sensitivities (percent change in annual runoff per degree change in annual temperature) range from declines of 2% to as much as 9% per degree Celsius increase at Lees Ferry. For some LSMs, small areas, primarily at midelevation, have increasing runoff with increasing temperature; however, on a spatial basis, most sensitivities are negative.
-
implications of global climate change for snowmelt hydrology in the twenty first century
Hydrological Processes, 2009Co-Authors: J C Adam, Alan F Hamlet, Dennis P LettenmaierAbstract:For most of the global land area poleward of about 40° latitude, snow plays an important role in the water cycle. The (seasonal) timing of runoff in these areas is especially sensitive to projected losses of snowpack associated with warming trends, whereas projected (annual) runoff volume Changes are primarily associated with Precipitation Changes, and to a lesser extent, with Changes in evapotranspiration (ET). Regional studies in the USA (and especially the western USA) suggest that hydrologic adjustments to a warming climate have been ongoing since the mid-twentieth century. We extend the insights extracted from the western USA to the global scale using a physically based hydrologic model to assess the effects of systematic Changes in Precipitation and temperature on snow-affected portions of the global land area as projected by a suite of global climate models. While annual (and in some cases seasonal) Changes in Precipitation are a key driver of projected Changes in annual runoff, we find, as in the western USA, that projected warming produces strong decreases in winter snow accumulation and spring snowmelt over much of the affected area regardless of Precipitation change. Decreased snowpack produces decreases in warm-season runoff in many mid- to high-latitude areas where Precipitation Changes are either moderately positive or negative in the future projections. Exceptions, however, occur in some high-latitude areas, particular in Eurasia, where Changes in projected Precipitation are large enough to result in increased, rather than decreased, snow accumulation. Overall, projected Changes in snowpack and the timing of snowmelt-derived runoff are largest near the boundaries of the areas that currently experience substantial snowfall, and at least qualitatively, they mirror the character of observed Changes in the western USA. Copyright © 2008 John Wiley & Sons, Ltd.
Chris S Renschler - One of the best experts on this subject based on the ideXlab platform.
-
modeling response of soil erosion and runoff to Changes in Precipitation and cover
Catena, 2005Co-Authors: M A Nearing, V G Jetten, Claire Baffaut, Olivier Cerdan, A Couturier, Mariano Hernandez, Le Y Bissonnais, M H Nichols, Joao Pedro Nunes, Chris S RenschlerAbstract:Global climate has changed over the past century. Precipitation amounts and intensities are increasing. in this study we investigated the response of seven soil erosion models to a few basic Precipitation and vegetation related parameters using common data from one humid and one semi-arid watershed. Perturbations were made to inputs for rainfall intensities and amounts, and to ground surface cover and canopy cover. Principal results were that: soil erosion is likely to be more affected than runoff by Changes in rainfall and cover, though both are likely to be significantly impacted; percent erosion and runoff will likely change more for each percent change in rainfall intensity and amount than to each percent change in either canopy or ground cover; Changes in rainfall amount associated with Changes in storm rainfall intensity will likely have a greater impact on runoff and erosion than simply Changes in rainfall amount alone; Changes in ground cover have a much greater impact on both runoff and erosion than Changes in canopy cover alone. The results do not imply that future Changes in rainfall will dominate over Changes in land use, since land use Changes can often be drastic. Given the types of Precipitation Changes that have occurred over the last century, and the expectations regarding Changes over the next century, the results of this study suggest that there is a significant potential for climate change to increase global soil erosion rates unless offsetting conservation measures are taken.
Agnes Ducharne - One of the best experts on this subject based on the ideXlab platform.
-
future Changes in Precipitation and impacts on extreme streamflow over amazonian sub basins
Environmental Research Letters, 2013Co-Authors: Matthieu Guimberteau, Josyane Ronchail, Jhan Carlo Espinoza, Matthieu Lengaigne, Benjamin Sultan, Jan Polcher, Guillaume Drapeau, Jeanloup Guyot, Agnes DucharneAbstract:Because of climate change, much attention is drawn to the Amazon River basin, whose hydrology has already been strongly affected by extreme events during the past 20 years. Hydrological annual extreme variations (i.e. low/high flows) associated with Precipitation (and evapotranspiration) Changes are investigated over the Amazon River sub-basins using the land surface model ORCHIDEE and a multimodel approach. Climate change scenarios from up to eight AR4 Global Climate Models based on three emission scenarios were used to build future hydrological projections in the region, for two periods of the 21st century. For the middle of the century under the SRESA1B scenario, no change is found in high flow on the main stem of the Amazon River (Obidos station), but a systematic discharge decrease is simulated during the recession period, leading to a 10% low-flow decrease. Contrasting discharge variations are pointed out depending on the location in the basin. in the western upper part of the basin, which undergoes an annual persistent increase in Precipitation, high flow shows a 7% relative increase for the middle of the 21st century and the signal is enhanced for the end of the century (12%). By contrast, simulated Precipitation decreases during the dry seasons over the southern, eastern and northern parts of the basin lead to significant low-flow decrease at several stations, especially in the Xingu River, where it reaches -50%, associated with a 9% reduction in the runoff coefficient. A 18% high-flow decrease is also found in this river. in the north, the low-flow decrease becomes higher toward the east: a 55% significant decrease in the eastern Branco River is associated with a 13% reduction in the runoff coefficient. The estimation of the streamflow elasticity to Precipitation indicates that southern sub-basins (except for the mountainous Beni River), that have low runoff coefficients, will become more responsive to Precipitation change (with a 5 to near 35% increase in elasticity) than the western sub-basins, experiencing high runoff coefficient and no change in streamflow elasticity to Precipitation. These projections raise important issues for populations living near the rivers whose activity is regulated by the present annual cycle of waters. The question of their adaptability has already arisen.
M A Nearing - One of the best experts on this subject based on the ideXlab platform.
-
modeling response of soil erosion and runoff to Changes in Precipitation and cover
Catena, 2005Co-Authors: M A Nearing, V G Jetten, Claire Baffaut, Olivier Cerdan, A Couturier, Mariano Hernandez, Le Y Bissonnais, M H Nichols, Joao Pedro Nunes, Chris S RenschlerAbstract:Global climate has changed over the past century. Precipitation amounts and intensities are increasing. in this study we investigated the response of seven soil erosion models to a few basic Precipitation and vegetation related parameters using common data from one humid and one semi-arid watershed. Perturbations were made to inputs for rainfall intensities and amounts, and to ground surface cover and canopy cover. Principal results were that: soil erosion is likely to be more affected than runoff by Changes in rainfall and cover, though both are likely to be significantly impacted; percent erosion and runoff will likely change more for each percent change in rainfall intensity and amount than to each percent change in either canopy or ground cover; Changes in rainfall amount associated with Changes in storm rainfall intensity will likely have a greater impact on runoff and erosion than simply Changes in rainfall amount alone; Changes in ground cover have a much greater impact on both runoff and erosion than Changes in canopy cover alone. The results do not imply that future Changes in rainfall will dominate over Changes in land use, since land use Changes can often be drastic. Given the types of Precipitation Changes that have occurred over the last century, and the expectations regarding Changes over the next century, the results of this study suggest that there is a significant potential for climate change to increase global soil erosion rates unless offsetting conservation measures are taken.
-
runoff and soil loss responses to Changes in Precipitation a computer simulation study
Journal of Soil and Water Conservation, 2002Co-Authors: F F Pruski, M A NearingAbstract:ABSTRACT: Changes in Precipitation have occurred over the past century and are expected to continue over the next century. These Changes will have significant implications for runoff, soil erosion, and conservation planning. This study was undertaken to investigate how runoff and soil erosion by water can be expected to be altered as a function of Changes in the average number of days of Precipitation per year and Changes in the amount and intensity of the rain that falls on a given day. The Water Erosion Prediction Project (WEPP) model was used to simulate erosion for three locations, three soils, three slopes, and four crops. Average annual Precipitation was changed ±10% and ±20% by changing either a) the number of wet days per year, b) the amount and intensity of Precipitation per day, or c) a combination of the two. Results indicated that, on average, each 1% change in average annual Precipitation induced a 1.28%, 2.50%, and 1.97% change in runoff and a 0.85%, 2.38%, and 1.66% change in soil loss for the three types of Precipitation Changes, respectively. Comparisons of the results of the soil-loss simulations to published relationships for Revised Universal Soil Loss Equation (RUSLE) R-factors in the United States suggest that the third option of changing both the number of wet days per year and the amount and intensity of Precipitation per day is the most realistic scenario for representing Changes in Precipitation for hydrologic studies.
Julie A Vano - One of the best experts on this subject based on the ideXlab platform.
-
seasonal hydrologic responses to climate change in the pacific northwest
Water Resources Research, 2015Co-Authors: Julie A Vano, Bart Nijssen, Dennis P LettenmaierAbstract:increased temperatures and Changes in Precipitation will result in fundamental Changes in the seasonal distribution of streamflow in the Pacific Northwest and will have serious implications for water resources management. To better understand local impacts of regional climate change, we conducted model experiments to determine hydrologic sensitivities of annual, seasonal, and monthly runoff to imposed annual and seasonal Changes in Precipitation and temperature. We used the Variable infiltration Capacity (VIC) land-surface hydrology model applied at 1/16° latitude-longitude spatial resolution over the Pacific Northwest (PNW), a scale sufficient to support analyses at the hydrologic unit code eight (HUC-8) basin level. These experiments resolve the spatial character of the sensitivity of future water supply to Precipitation and temperature Changes by identifying the seasons and locations where climate change will have the biggest impact on runoff. The PNW exhibited a diversity of responses, where transitional (intermediate elevation) watersheds experience the greatest seasonal shifts in runoff in response to cool season warming. We also developed a methodology that uses these hydrologic sensitivities as basin-specific transfer functions to estimate future Changes in long-term mean monthly hydrographs directly from climate model output of Precipitation and temperature. When principles of linearity and superposition apply, these transfer functions can provide feasible first-order estimates of the likely nature of future seasonal streamflow change without performing downscaling and detailed model simulations.
-
hydrologic sensitivities of colorado river runoff to Changes in Precipitation and temperature
Journal of Hydrometeorology, 2012Co-Authors: Julie A Vano, Dennis P LettenmaierAbstract:The Colorado River is the primary water source for much of the rapidly growing southwestern United States. Recent studies have projected reductions in Colorado River flows from less than 10% to almost 50% by midcentury because of climate change—a range that has clouded potential management responses. These differences in projections are attributable to variations in climate model projections but also to differing land surface model (LSM) sensitivities. This second contribution to uncertainty—specifically, variations in LSM runoff change with respect to Precipitation (elasticities) and temperature (sensitivities)—are evaluated here through comparisons of multidecadal simulations from five commonly used LSMs (Catchment, Community Land Model, Noah, Sacramento Soil Moisture Accounting model, and Variable infiltration Capacity model) all applied over the Colorado River basin at 1/88 latitude by longitude spatial resolution. The annual elasticity of modeled runoff (fractional change in annual runoff divided by fractional change in annual Precipitation) at Lees Ferry ranges from two to six for the different LSMs. Elasticities generally are higher in lower Precipitationand/orrunoffregimes;hence,the highestvaluesare formodelsbiasedlow in runoffproduction,and the range of elasticities is reduced to two to three when adjusted to current runoff climatology. Annual temperature sensitivities (percent change in annual runoff per degree change in annual temperature) range from declines of 2% to as much as 9% per degree Celsius increase at Lees Ferry. For some LSMs, small areas, primarily at midelevation, have increasing runoff with increasing temperature; however, on a spatial basis, most sensitivities are negative.