Sensitivity Of Streamflow Research Articles

Coupled modelling of glacier and streamflow response to future climate scenarios

This study investigated the sensitivity of streamflow to changes in climate and glacier cover for the Bridge River basin, British Columbia, using a semi‐distributed conceptual hydrological model coupled with a glacier response model. Mass balance data were used to constrain model parameters. Climate scenarios included a continuation of the current climate and two transient GCM scenarios with greenhouse gas forcing. Modelled glacier mass balance was used to re‐scale the glacier every decade using a volume‐area scaling relation. Glacier area and summer streamflow declined strongly even under the steady‐climate scenario, with the glacier retreating to a new equilibrium within 100 years. For the warming scenarios, glacier retreat continued with no evidence of reaching a new equilibrium. Uncertainty in parameters governing glacier melt produced uncertainty in future glacier retreat and streamflow response. Where mass balance information is not available to assist with calibration, model‐generated future scenarios will be subject to significant uncertainty.

Assessing the effects of climate change on the hydrological regime of the Limay River basin

The electricity generation capacity in the Limay River basin is approximately 26% of the total electrical power generation in Argentina. Assessing the potential effects of climate change on the hydrological regime of this basin is an important issue for water resources management. This study explores the presence of trends in streamflow series, evaluates climate sensitivity and studies the effects on the flow regime of predicted changes in precipitation in the basin. In order to identify and quantify changes in observed streamflow series, the Mann–Kendall test, with a modification for autocorrelated data, and an estimator of the magnitude of the trend are applied. In order to evaluate the sensitivity of streamflow to changes in climate, the concept of elasticity is used. Precipitation elasticity of streamflow is used to quantify the sensitivity of streamflow to changes in precipitation and is estimated using a power law model and a linear statistical model in two sub-basins, Alumine and Nahuel Huapi. The effects on flow regime of the predicted changes in precipitation under different scenarios are studied. Climatic results for different scenarios of growth in greenhouse gases from some General Circulation Models are used as inputs into the proposed models. The analysis identifies decreasing trends in mean and minimum annual flows and in the low flow season. The estimates of the precipitation elasticity imply that changes in precipitation produce similar changes in streamflow and the climatic results for different scenarios show that the variations are moderate.

Assessing the impact of climate variability and human activities on streamflow from the Wuding River basin in China

AbstractLocated in the Loess Plateau of China, the Wuding River basin (30 261 km2) contributes significantly to the total sediment yield in the Yellow River. To reduce sediment yield from the catchment, large‐scale soil conservation measures have been implemented in the last four decades. These included building terraces and sediment‐trapping dams and changing land cover by planting trees and improving pastures. It is important to assess the impact of these measures on the hydrology of the catchment and to provide a scientific basis for future soil conservation planning. The non‐parametric Mann–Kendall–Sneyers rank test was employed to detect trends and changes in annual streamflow for the period of 1961 to 1997. Two methods were used to assess the impact of climate variability on mean annual streamflow. The first is based on a framework describing the sensitivity of annual streamflow to precipitation and potential evaporation, and the second relies on relationships between annual streamflow and precipitation. The two methods produced consistent results. A significant downward trend was found for annual streamflow, and an abrupt change occurred in 1972. The reduction in annual streamflow between 1972 and 1997 was 42% compared with the baseline period (1961–1971). Flood‐season streamflow showed an even greater reduction of 49%. The streamflow regime of the catchment showed a relative reduction of 31% for most percentile flows, except for low flows, which showed a 57% reduction. The soil conservation measures reduced streamflow variability, leading to more uniform streamflow. It was estimated that the soil conservation measures account for 87% of the total reduction in mean annual streamflow in the period of 1972 to 1997, and the reduction due to changes in precipitation and potential evaporation was 13%. Copyright © 2007 John Wiley & Sons, Ltd.

Regime‐dependent streamflow sensitivities to Pacific climate modes cross the Georgia–Puget transboundary ecoregion

AbstractThe Georgia Basin–Puget Sound Lowland region of British Columbia (Canada) and Washington State (USA) presents a crucial test in environmental management due to its combination of abundant salmonid habitat, rapid population growth and urbanization, and multiple national jurisdictions. It is also hydrologically complex and heterogeneous, containing at least three streamflow regimes: pluvial (rainfall‐driven winter freshet), nival (melt‐driven summer freshet), and hybrid (both winter and summer freshets), reflecting differing elevation ranges within various watersheds. We performed bootstrapped composite analyses of river discharge, air temperature, and precipitation data to assess El Niño–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) impacts upon annual hydrometeorological cycles across the study area. Canadian and American data were employed from a total of 21 hydrometric and four meteorological stations. The surface meteorological anomalies showed strong regional coherence. In contrast, the seasonal impacts of coherent modes of Pacific circulation variability were found to be fundamentally different between streamflow regimes. Thus, ENSO and PDO effects can vary from one stream to the next within this region, albeit in a systematic way. Furthermore, watershed glacial cover appeared to complicate such relationships locally; and an additional annual streamflow regime was identified that exhibits climatically driven non‐linear phase transitions. The spatial heterogeneity of seasonal flow responses to climatic variability may have substantial implications to catchment‐specific management and planning of water resources and hydroelectric power generation, and it may also have ecological consequences due to the matching or phase‐locking of lotic and riparian biological activity and life cycles to the seasonal cycle. The results add to a growing body of literature suggesting that assessments of the streamflow impacts of ocean–atmosphere circulation modes must accommodate local hydrological characteristics and dynamics. Copyright © 2007 John Wiley & Sons, Ltd. The copyright in Paul H. Whitfield's contribution belongs to the Crown in right of Canada and such copyright material is reproduced with the permission of Environment Canada.

Estimation of rainfall elasticity of streamflow in Australia

Estimates of rainfall elasticity of streamflow in 219 catchments across Australia are presented. The rainfall elasticity of streamflow is defined here as the proportional change in mean annual streamflow divided by the proportional change in mean annual rainfall. The elasticity is therefore a simple estimate of the sensitivity of long-term streamflow to changes in long-term rainfall, and is particularly useful as an initial estimate of climate change impact in land and water resources projects. The rainfall elasticity of streamflow is estimated here using a hydrological modelling approach and a nonparametric estimator. The results indicate that the rainfall elasticity of streamflow (ϵ P ) in Australia is about 2.0–3.5 (observed in about 70% of the catchments), that is, a 1% change in mean annual rainfall results in a 2.0–3.5% change in mean annual streamflow. The rainfall elasticity of streamflow is strongly correlated to runoff coefficient and mean annual rainfall and streamflow, where streamflow is more sensitive to rainfall in drier catchments, and those with low runoff coefficients. There is a clear relation-ship between the ϵ P values estimated using the hydrological modelling approach and those estimated using the nonparametric estimator for the 219 catchments, although the values estimated by the hydrological modelling approach are, on average, slightly higher. The modelling approach is useful where a detailed study is required and where there are sufficient data to reliably develop and calibrate a hydrological model. The nonparametric estimator is useful where consistent estimates of the sensitivity of long-term streamflow to climate are required, because it is simple to use and estimates the elasticity directly from the historical data. The nonparametric method, being model independent, can also be easily applied in comparative studies to data sets from many catchments across large regions.

Effects of Averaging and Separating Soil Moisture and Temperature in the Presence of Snow Cover in a SVAT and Hydrological Model for a Southern Ontario, Canada, Watershed

Abstract The energy and water balances at the earth's surface are dramatically influenced by the presence of snow cover. Therefore, soil temperature and moisture for snow-covered and snow-free areas can be very different. In computing these soil state variables, many land surface schemes in climate models do not explicitly distinguish between snow-covered and snow-free areas. Even if they do, some schemes average these state variables to calculate grid-mean energy fluxes and these averaged state variables are then used at the beginning of the next time step. This latter approach introduces a numerical error in that heat is redistributed from snow-free areas to snow-covered areas, resulting in a more rapid snowmelt. This study focuses on the latter approach and examines the sensitivity of soil moisture and streamflow to the treatment of the soil state variables in the presence of snow cover by using WATCLASS, a land surface scheme linked with a hydrologic model. The model was tested for the 1993 snowmelt period on the Upper Grand River in Southern Ontario, Canada. The results show that a more realistic simulation of streamflow can be obtained by keeping track of the soil states in snow-covered and snow-free areas.

SLURP모형의 증발산 모형에 대한 평가

수문 모형들은 물 순환에 있어서의 지표 성분을 모의하고 기후 변동이 수자원에 미치는 영향을 평가하는데 메커니즘을 제공한다. 이러한 모형들에 있어서 증발산량(Evapoanspiration, ET)은 매우 중요한 요소이다. 본 연구에서는 SLURP 모형에서 증발산량 산정을 위하여 제시하고 있는 FAO Penman-Monteith, Morton CRAE(Complementary Relationship Area Evapotranspiration), Spittlehouse-Black, Granger, the Linacre 등, 5 가지의 방법론이 일 하천유출량에 미치는 영향을 분석하고, 각 증발산 방법과 SLURP 모형의 매개변수와의 민감도 분석을 실시하였다. 분석 결과, 본 논문에서는 SLURP 모형을 이용하여 용담댐 유역의 일 유출량을 모의할 경우 여러 증발산 모형 중 Morton CRAE 모형 이 가장 적합함을 확인하였다. Hydrological models simulate the land phase components of the water cycle and provide a mechanism for evaluating the effects of climatic variation and change on water resources. Evapotranspiration(ET) is a critical process within hydrological models. This study evaluates five different methods for estimating ET in the SLURP(Semi-distributed Land Use Runoff Process)model, in the Yongdam basin. The five ET methods were the FAO Penman-Monteith, Morton CRAE (Complementary Relationship Area Evapotranspiration), the Spittlehouse-Black, the Granger, the Linacre model. We evaluated the five ET models, based on the ability of SLURP model to simulate daily streamflow, and How the five ET methods influence the sensitivity of simulated streamflow to changes in key model parameters and validation SLURP independently for each ET methods. The results showed that the Merton CRAE model had more physical significance and gave better agreement simulated stream flow and recorded flows. It noted that the Morton CRAE model might be more appropriate for the simulation of the actual evapotranspiration in SLURP hydrologic model.

Hydroclimatology of the continental United States

The overall water balance and the sensitivity of watershed runoff to changes in climate are investigated using national databases of climate and streamflow for 1,337 watersheds in the U.S. We document that 1% changes in precipitation result in 1.5–2.5% changes in watershed runoff, depending upon the degree of buffering by storage processes and other factors. Unlike previous research, our approach to estimating climate sensitivity of streamflow is nonparametric and does not depend on a hydrologic model. The upper bound for precipitation elasticity of streamflow is shown to be the inverse of the runoff ratio. For over a century, investigators [Pike, 1964; Budyko, 1974; Ol'dekop, 1911; and Schreiber, 1904] have suggested that variations in watershed aridity alone are sufficient to predict spatial variations in long‐term watershed runoff. We document that variations in soil moisture holding capacity are just as important as variations in watershed aridity in explaining the mean and variance of annual watershed runoff.

Climate elasticity of streamflow in the United States

Precipitation elasticity of streamflow, ϵP, provides a measure of the sensitivity of streamflow to changes in rainfall. Watershed model‐based estimates of ϵP are shown to be highly sensitive to model structure and calibration error. A Monte Carlo experiment compares a nonparametric estimator of ϵP with various watershed model‐based approaches. The nonparametric estimator is found to have low bias and is as robust as or more robust than alternate model‐based approaches. The nonparametric estimator is used to construct a map of ϵP for the United States. Comparisons with 10 detailed climate change studies reveal that the contour map of ϵP introduced here provides a validation metric for past and future climate change investigations in the United States. Further investigations reveal that ϵP tends to be low for basins with significant snow accumulation and for basins whose moisture and energy inputs are seasonally in phase with one another. The Budyko hypothesis can only explain variations in ϵP for very humid basins.

Potential effects of climate change and urbanization on mean annual streamflow in the United States

Estimates of the impacts of climate change on streamflow generally have not included concurrent effects of urbanization. A statistical analysis of historical streamflow, climate, and population data for 39 urbanizing and 21 nearby rural basins in four regions of the United States was used to estimate the future effects of climate change and urbanization on mean annual streamflow. Basins were located generally at lower elevations where streamflow was dominated by rainfall rather than snowmelt. Rural basins showed predicted average changes in mean annual streamflow ranging between +24 and −49% for the specific climate change scenarios tested (precipitation changes −20 to +20%, temperature changes 0°C to +4°C). Urbanization increased mean annual streamflow in rough proportion to average cumulative changes in population density on the basins, equivalent to an average flow increase of 103% with complete watershed urbanization. Urbanization also appeared to reduce the sensitivity of mean annual streamflow to temperature changes compared to mean flow response on rural basins. No significant regional differences in mean flow response to climate change and urbanization were found. Despite the uncertainty in predicting future streamflow with models based upon past records, urbanization appears potentially capable of significantly offsetting flow declines or augmenting flow increases caused by climate change.

Observed Sacramento Basin streamflow response to precipitation and temperature changes and its relevance to climate impact studies

Observational studies of Sacramento Basin annual mean streamflow response to precipitation and temperature indicate that streamflow amounts in the basin are strongly sensitive to precipitation, but virtually insensitive to mean seasonal temperature. This result is in accord with studies of the climate mean sensitivity of streamflow amount to changes in climatological mean precipitation and temperature as simulated by conceptual hydrological models of the basin. Simpler regression models of the Sacramento Basin show a strong dependence of streamflow amount on temperature, which is not evident in the observation-based annual mean streamflow sensitivity. The interannual variability in Sacramento Basin streamflow response to precipitation exhibits substantial nonlinearity in that the partitioning of precipitation to runoff strongly depends on the precipitation volume. During very wet years in the basin, streamflow response to precipitation exhibits a proportionally greater change (increase) than during normal or dry years. For most dry years in the basin the streamflow response to precipitation is fairly linear. However, on the tails of droughts the streamflow response to precipitation is diminished relative to other dry years. This implies that a shift to a much drier or more drought-prone climate would result in a more substantial reduction in streamflow amounts than might at present be expected from observations of streamflow responses in isolated dry years. This conclusion assumes no changes in the features controlling water retention in the basin, which is an important issue to be addressed in basin climate change studies.

THE SENSITWITY OF NORTHERN SIERRA NEVADA STREAMFLOW TO CLIMATE CHANGE1

ABSTRACT: The sensitivity of streamflow to climate change was investigated in the American, Carson, and Truckee River Basins, California and Nevada. Nine gaging stations were used to represent streamflow in the basins. Annual models were developed by regressing 1961–1991 streamflow data on temperature and precipitation. Climate‐change scenarios were used as inputs to the models to determine streamflow sensitivities. Climate‐change scenarios were generated from historical time series by modifying mean temperatures by a range of +4°C to—4°C and total precipitation by a range of +25 percent to ‐25 percent. Results show that streamflow on the warmer, lower west side of the Sierra Nevada generally is more sensitive to temperature and precipitation changes than is streamflow on the colder, higher east side. A 2°C rise in temperature and a 25‐percent decrease in precipitation results in stream‐flow decreases of 56 percent on the American River and 25 percent on the Carson River. A 2°C decline in temperature and a 25‐percent increase in precipitation results in streamflow increases of 102 percent on the American River and 22 percent on the Carson River.

Sensitivity of streamflow in the Colorado Basin to climatic changes

Changes in regional temperature and precipitation expected to occur as a result of the accumulation of greenhouse gases may have significant impacts on water resources. We use a conceptual hydrologic model, developed and operated by the National Weather Service, to study the sensitivity of surface runoff in several sub-basins of the Colorado River to these changes. Increases in temperature of 2°C decrease mean annual runoff by 4–12%. A temperature increase of 4°C decreases mean annual runoff by 9–21%. Increases or decreases in annual precipitation of 10–20% result in corresponding changes in mean annual runoff of approximately 10–20%. For the range of scenarios studied, these results suggest that runoff in the basin is somewhat more sensitive to changes in precipitation than to changes in temperature. Seasonal changes were also observed, with peak runoff shifting from June to April or May. Fall and winter flows generally increase, whereas spring and summer flows decrease in most of the scenarios studied. These changes are attributed to an increase of the ratio of rain to snow and to a higher snowline. Although these results suggest that streamflow in the Colorado Basin is less sensitive to climatic changes than previous statistical studies have indicated, the magnitude of possible changes is nonetheless sufficiently great to have significant environmental, economic, and political implications.

Hydrologic problems concerning the runoff in headwater regions

In this paper are discussed some of the concepts of watershed hydrology as related to surface, subsurface, and ground‐water runoff. Data from Swiss and other watershed studies illustrate that true ground‐water discharge may form the major part of flood flows, with minor or no contributions by surface runoff. Results of experiments with sand troughs to determine the effect of aquifer length are used to explain apparent anomalies in the comparison of the two Emmental watersheds. It is postulated that the length of the aquifer is a factor controlling ground‐water storage and sensitivity of stream flow to rainfall. In the sand troughs and the Swiss watersheds the same volume of ground‐water storage did not always produce the same runoff rate. The explanation is that outflow is controlled by the rate of filling. Short rains of high intensity, even without any surface runoff, will produce crests more pointed than those of rains of longer duration and lower intensity.