Amount Of Streamflow Research Articles

Impact of Climate Change on Reservoir Operation during the Dry Season in the Pearl River Basin

Climate change has far-reaching impacts that have created new challenges for water resource management. As an important measure to coordinate the relationship between society, economy, and environment, reservoir scheduling can reduce the future impact of climate change. It is, therefore, important to investigate the impacts of scheduling on reservoir operation. In this study, a reservoir system in the Pearl River Basin was selected to explore these impacts. Results show that the basin temperature significantly and abruptly increased in 2000, and precipitation and streamflow changed abruptly in 1983 and 1992. Historically, climate change has increased power generation, increased the risks to water supply security and ecological protection, and altered the relationship between power generation and ecological protection objectives. Based on 28 global climate models, the rank scoring method, Delta statistical downscaling, and the SWAT model, three emission scenarios (RCP2.6, RCP4.5, and RCP8.5) in CMCC-CM were evaluated to assess the climate change impact. In the future, the temperature will continue to exhibit an increasing trend, and the amount and distribution of streamflow will be altered. Although climate change will increase power generation in the dry season, it will also bring about new challenges for ecological protection and water supply security. Accordingly, the Datengxia Reservoir operating rules may require significant amendments.

Investigation of the propagation of meteorological to hydrological drought and water required to recover from drought over Ethiopian basins

Abstract This study investigates drought propagation from meteorological to hydrological and streamflow required to recover from drought in four sub-basins: Genale, Tekeze, Awash, and Baro basins of Ethiopia. Due to limited observed streamflow data, the soil moisture accounting and routing (SMAR) model was used to extend the streamflow data for each sub-basin from 1985 to 2017. Drought characteristics in terms of duration, severity, and onset/offset of drought and propagation time at different time scales are investigated using run theory and Pearson correlation, respectively. Two Archimedean copulas (Clayton and Gumbel) are used to identify the joint return period between drought duration and severity and the amount of streamflow required to recover from hydrological drought for each sub-basin. Our results revealed that drought frequency has increased over most sub-basins over the last two decades. The propagation time from meteorological drought to hydrological drought is shorter over the Tekeze sub-basin (1–3 months); however, Genale and Awash sub-basin show 3- to 6-month propagation time. The more extended propagation time is seen over the Baro sub-basin (6–9 months). The required amount of water for drought recovery estimation shows a linear relationship between the duration of the drought and the amount required.

Impact of climate change on future precipitation amounts, seasonal distribution, and streamflow in the Omo-Gibe basin, Ethiopia

This study projected the impact of climate change on the amount of precipitation, seasonal distribution, and streamflow of the Omo-gibe basin, Ethiopia. Projections of climate change using the results of high-resolution multimodal ensembles from fifteen regional climate models (RCMs) of the Coordinated Regional Climate Reduction Experiment (CORDEX)-Africa were statistically downscaled and bias-adjusted using a quantile mapping approach. Precipitation and temperature were projected under RCP 8.5 and RCP 4.5 emission scenarios. Climate and streamflow projections from a mean ensemble of RCMs in the near future (2025–2050), medium future (2051–2075), and far future (2076–2100) were compared to the reference (1989–2019). Mann-Kendall (MK) trend testing was used to determine if a change is statistically significant and to detect trends in temperature, precipitation, and streamflow. The Soil and Water Assessment Tool (SWAT) hydrological model was used to project the impact of climate change on the streamflow. According to RCP4.5 and RCP8.5, the emission scenarios predicted significant positive (rising) temperature, but significant negative (decreasing) precipitation and streamflow. The average temperature projected increases range from 2.40-3.34 °C under the RCP 4.5 emission scenarios and 2.6–4.54 °C under the RCP 8.5 emission scenarios. Annual average precipitation projected decreases range between 10.77-13.11% under the RCP 4.5 emission scenario, while the RCP 8.5 emission scenarios decrease range between 11.10-13.86% in the rainy summer season (June–August) and the irregular rain season (March–May). Projected annual average streamflow decrease range between 7.08-10.99% under the RCP 4.5 emission scenarios and 10.98–12.88% under the RCP 8.5 emission scenarios. Results on projected temperature increases and reductions in precipitation and streamflow will help to develop effective adaptation measures to reduce the ongoing impacts of climate change and draw up long-term water resource management plans in the river basin. Both the results and the multidisciplinary approach will be vital to irrigation and hydropower project planners.

Unravelling runoff processes in Andean basins in northern Ecuador through hydrological signatures

AbstractStreamflow is the runoff response integrated in space and time over a complex system involving climatic and catchment physiographic factors. In the Andes, accelerating runoff process understanding is hampered by the inability to quantify heterogeneity of surface and subsurface catchment properties. Here, we present a statistical approach based on regression models and correlation analysis that links hydrological signatures and catchment properties to unveil processes in a set of volcanic mountain catchments (latitude 0°30'N) in Ecuador. The catchments represent form and function diversity in the same hydrological unit. We found that despite of similar atmospheric‐water inputs the water yield in the north‐east region is about 5× larger than in the south‐west region and their flow regimes are asymmetric. The soil‐bedrock interface and lithology exert a first‐order control on hydrologic partitioning, and this allowed us to hypothesize two hydrological mechanisms. Firstly, in the north‐east region, the perennial streamflow is associated with seasonal rainfall patterns, and subsequent drainage processes taking place at the surface and subsurface level. The amount of streamflow is related to landform characteristics, high canopy density and root development of forest as well as water holding capacity of organic soils. From a mechanistic standpoint, the low concentration time, steep slopes and shallow infiltration limited by high‐consolidated deposits of sedimentary and volcanics suggest a lateral movement of the flow. Secondly, in the south‐west region the streamflow regime is mostly groundwater‐dependent and it becomes seasonally enhanced by rainfall. Larger seasonal variations of precipitation and temperature result into enhanced evapotranspiration in the drier months, limiting shallow soil infiltration. Under the soil layers, highly permeable pyroclastic deposits and andesitic lavas promote deep percolation. The results highlight the degree of dissimilarity of hydrological processes in Andean settings, but unravelling their complexity seems plausible using streamflow signatures and causal explanatory models.

Sediment and Nutrient Transfer from an Inter-montane Agricultural Catchment in Himachal Himalayas of Northwestern India

Abstract The present study aims to quantify the transfer of sediments and nutrients from an inter-montane agricultural catchment located in lower Himachal Himalayas of north western India. The study is based on long-term water quality data for July to September months for the period 2004 to 2010. The data for this study has been procured from Bhakra Beas Management Board, Sundernagar. The study has revealed a high degree of transfer and variability in sediment and nutrient concentrations, loads and yields, causing pollution downstream. The sediment concentrations have varied from 10 to 8117 mg/l with a variability of 54%. The micro nutrients concentrations have varied from 0.03 to 0.41 mg/l for zinc, 0.13 to 6.64 mg/l for iron and 0.02 to 1.30 mg/l for copper. Among the macro nutrients, highest concentrations have been observed for sulphate (11.81 mg/l) followed by phosphate (0.97 mg/l) and nitrate (0.40 mg/l). The correlation analysis has revealed that sediment and nutrient flux from the catchment are dependent on amount of stream flow. However, the extent of correlations has been, in general, low or non-significant. The findings of this study will have key implications for future sediment and nutrient transfer from agricultural catchments of north western Himalayan region.

Quantifying the base flow of the Colorado River: its importance in sustaining perennial flow in northern Arizona and southern Utah (USA)

Water in the Colorado River, USA, is known to be a highly over-allocated resource, yet managers and decision makers rarely consider one of the most important contributions to the existing water in the river, i.e. groundwater. This oversight may result from the contrasting results of base-flow studies conducted on the amount of streamflow into the Colorado River sourced from groundwater. Some studies rule out the significance of groundwater contribution, while others show groundwater contributing the majority of flow to the river. This study uses new and extant instrumented data (not indirect methods) to quantify the groundwater base-flow contribution to surface flow. The precipitation, streamflow, and base flow of 10 remote subbasins of the Colorado Plateau in southern Utah and northern Arizona were examined in detail. These tributaries have an annual average base-flow discharge of 0.45 km3/year (367,000 acre-feet per year) with an average base-flow fraction of 72% summing to more than 3% of the mean flow of the Colorado River at Phantom Ranch. The groundwater storage trend of the Colorado River Basin when measured with remote sensing is declining; however, when utilizing instrumented data, the average annual base-flow trend in the study area remains constant. This trend suggests that base-flow signatures in streams may have a delayed response from the decline observed in groundwater storage from remote sensing. The simple extant data measurement methods employed in this study can be applied to the entire drainage basin, revealing the quantity of base flow throughout the basin to better inform water resource management.

Evaluating Mismatches between Legislation and Practice in Maintaining Environmental Flows

Freshwater is essential to human communities and stream ecosystems, and governments strive to manage water to meet the needs of both people and ecosystems. Balancing competing water demands is challenging, as freshwater resources are limited and their availability varies through time and space. One approach to maintain this balance is to legally mandate that a specified amount of stream flow be maintained for stream ecosystems, known as an environmental flow. But laws and regulations do not necessarily reflect what happens in practice, potentially to the detriment of communities and natural systems. Through a case study of Puerto Rico, we investigated whether water management in practice matches legislative mandates and explored potential mismatch drivers. We focused on two governance targets—equitable allocation and water use efficiency—and assessed whether they are enshrined in the law (de jure) and how they manifest in practice (de facto). We also explored agency accountability through identifying agency structure and whether consequences are enforced for failing to carry out responsibilities. Our results indicate there are mismatches between how freshwater is governed by law and what occurs in practice. This study suggests that agency accountability may be necessary to consider when developing environmental flow legislation that will effectively achieve ecological outcomes.

The Impacts of Water Cycle Components on Streamflow in a Changing Climate of Korea: Historical and Future Trends

This paper investigates the historical and future trends in water balance components and their impacts on streamflow. The trend analyses were applied to the daily climatic and hydrologic variables from 109 subbasins in Korea during the historical period and future period obtained by a multimodel ensemble of 13 global circulation models (GCMs) of the Coupled Model Intercomparison Project, Phase 5 (CMIP5). A calibrated hydrologic model, the precipitation-streamflow modeling system (PRMS) model, was applied to obtain hydrologic data. The results revealed apparent trends in streamflow, with increases in spring and decreases in the other seasons during the historical period. The reduction (or increase) in the amount of streamflow was counterbalanced by the reduction (or increase) in precipitation, groundwater, and soil moisture, which was mainly impacted by the increase (or reduction) in actual evapotranspiration. However, opposite trends are projected for the future period for streamflow and water cycle components, in which spring and winter are projected to have increasing trends mostly counterbalanced by the decreasing trends in precipitation and groundwater. The reasons for the reduction in streamflow include elevated evapotranspiration compared to precipitation, reduced soil moisture, and a significant decrease in groundwater recharge. In addition, the results of the seasonal variability among basins revealed higher variability in summer for the historical period and in winter for the future period, with maximum variability in the Sumjin River basin, indicating that streamflow fluctuated more strongly in the Sumjin River basin during the historical and future periods.

The stream evolution triangle: Integrating geology, hydrology, and biology

AbstractThe foundations of river restoration science rest comfortably in the fields of geology, hydrology, and engineering, and yet, the impetus for many, if not most, stream restoration projects is biological recovery. Although Lane's stream balance equation from the mid‐1950s captured the dynamic equilibrium between the amount of stream flow, the slope of the channel, and the amount and calibre of sediment, it completely ignored biology. Similarly, most of the stream classification systems used in river restoration design today do not explicitly include biology as a primary driver of stream form and process. To address this omission, we cast biology as an equal partner with geology and hydrology, forming a triumvirate that governs stream morphology and evolution. To represent this, we have created the stream evolution triangle, a conceptual model that explicitly accounts for the influences of geology, hydrology, and biology. Recognition of biology as a driver leads to improved understanding of reach‐scale morphology and the dynamic response mechanisms responsible for stream evolution and adjustment following natural or anthropogenic disturbance, including stream restoration. Our aim in creating the stream evolution triangle is not to exclude or supersede existing stream classifications and evolutionary models but to provide a broader “thinking space” within which they can be framed and reconsidered, thus facilitating thought outside of the alluvial box.

Evaluation of the Water-Storage Capacity of Bryophytes along an Altitudinal Gradient from Temperate Forests to the Alpine Zone

Forests play crucial roles in regulating the amount and timing of streamflow through the water storage function. Bryophytes contribute to this increase in water storage owing to their high water-holding capacity; however, they might be severely damaged by climate warming. This study examined the water storage capacity (WSC) of bryophytes in forests in the mountainous areas of Japan. Sampling plots (100 m2) were established along two mountainous trails at 200-m altitude intervals. Bryophytes were sampled in these plots using 100-cm2 quadrats, and their WSC was evaluated according to the maximum amount of water retained in them (WSC-quadrat). The total amount of water in bryophytes within each plot (WSC-plot) was then calculated. The WSC-quadrat was affected by the forms of bryophyte communities (life forms) and their interactions, further influencing soil moisture. The WSC-quadrat did not show any significant trend with altitude, whereas, the highest WSC-plot values were obtained in subalpine forests. These changes to WSC-plot were explained by large differences in bryophyte cover with altitude. As the WSC controlled by the life forms might be vulnerable to climate warming, it can provide an early indicator of how bryophyte WCS and associated biological activities are influenced.

Analisis Potensi Pengembangan Pembangkit Listrik Tenaga Mikrohidro Di Kabupaten Bone Bolango

Energy is a major need in human life, but along with the population growth will be the availability of electrical energy especially that from fossil fuels are being reduced and insufficient for the needs of small-scale electric power listrik.Pembangkit potential as an alternative to fossil energy sources namely renewable micro hydro power plant availability of electricity in remote villages in the district of Bone Bolango is alarming, so it was done research on Analysis of Potential Development of micro hydro power plant (MHP) in Bone regency Bolango. This study aims to provide an overview and preliminary information on the potential of hydropower as a basis for planning and development of micro hydro power plant. In this research will be outlined potential sites for the development of MHP with power potential, specifications turbindan civilian buildings. Measurement of power was awakened by the amount of streamflow in Mongiilo Desa Ulu Subdistrict Bolango Bone Bolango District. Debit analyzed based on observation of the flow rate by using a current meter. From the analysis of the amount of power potential in getting aroused in the research area of 289,935Kw with ideal flow 12.14 m3 / sec, the average efficiency of 65% with the plan fell 3.75 m high. This power is sufficient magnitude elektrifitas needs of residents in the study area that is equal to 65kW.

Stream temperature response to climate change and water diversion activities

Stream temperature is an important control of many in-stream processes. There is rising concern about increases in stream temperature with projected climate changes and human-related water activities. Here, we investigate the responses to climate change and water diversions in Eel River basin. The increase in stream temperatures is considered to be the result of changes in air temperature, the proportion of base flow and the amount of stream flow derived from historical and future simulations using the integrated VIC hydrologic model and ANN stream temperature model. The results show that stream temperature will increase throughout the basin in the future under two climate change representative concentration pathways (RCPs 4.5 and 8.5) and will also be influenced by the water diversion activities schedules. Specifically, the stream temperature increases, in the late twenty-first century under RCP8.5 scenarios, from 1.20 to 2.40 °C in summer and from 0.58–3.46 °C in winter respectively; Water diversion activities in Eel River Basin can increase nearly 1 °C in stream temperature. Therefore, both climate change and water diversion activities can substantially cause the rise of more than 2 °C in stream temperature. In conclusion, stream temperature is mainly sensitive to the proportion of base flow in summer, but also the change of the amount of stream flow in winter in our case study area. In addition, it should be noted that the low intensity irrigation schedule has lower impacts on increasing stream temperature, whereas the high intensity irrigation schedule will further exacerbate the rise of stream temperature. Understanding the different impacts of climate change scenarios and irrigation schedules on stream temperature can help identify climate-sensitive regions, climate-sensitive seasons and water diversion schedules as well as assist in planning for climate change and social adaptive management.

Changes in Stream Flow and Their Relationships with Climatic Variations and Anthropogenic Activities in the Poyang Lake Basin, China

The Poyang Lake Basin has been suffering from severe water problems such as floods and droughts. This has led to great adverse impacts on local ecosystems and water resource utilization. It is therefore important to understand stream flow changes and their driving factors. In this paper, the dynamics of stream flow and precipitation in the Poyang Lake Basin between 1961 and 2012 were evaluated with the Mann–Kendall test, Theil–Sen approaches, Pettitt test, and Pearson’s correlation. Stream flow was measured at the outlets of five major tributaries of Poyang Lake, while precipitation was recorded by fourteen meteorological stations located within the Poyang Lake Basin. Results showed that annual stream flow of all tributaries and the precipitation over the study area had insignificant (P > 0.1) temporal trends and change points, while significant trends and shifts were found in monthly scale. Stream flow concentration indices (SCI) at Waizhou, Meigang, and Wanjiabu stations showed significant (P < 0.05) decreasing trends with change points emerging in 1984 at Waizhou and 1978 at Wanjiabu, while there was no significant temporal trend and change point detected for the precipitation concentration indices (PCI). Correlation analysis indicated that area-average stream flow was closely related to area-average precipitation, but area-average SCI was insignificantly correlated with area-average PCI after change point (1984). El Niño/Southern Oscillation (ENSO) had greater impacts on stream flow than other climate indices, and La Niña events played a more important role in stream flow changes than EI Niño. Human activities, particularly in terms of reservoir constructions, largely altered the intra-annual distribution of stream flow but its effects on the amount of stream flow were relatively low. Results of this study provided a useful reference to regional water resource management and the prevention of flood and drought disasters.

SWAT hydrologic model parameter uncertainty and its implications for hydroclimatic projections in snowmelt-dependent watersheds

Summary The effects of climate change on water resources have been studied extensively throughout the world through the use of hydrologic models coupled with General Circulation Model (GCM) output or climate sensitivity scenarios. This paper examines the effects of hydrologic model parameterization uncertainty or equifinality, where multiple unique hydrologic model parameter sets can result in adequate calibration metrics, on hydrologic projections from downscaled GCMs for three snowmelt-dependent watersheds (upper reaches of the Clearwater, Gunnison, and Sacramento River watersheds) in the western United States. The hydrologic model used in this study is the Soil and Water Assessment Tool (SWAT) and is calibrated for discharge at the watershed outlet in each watershed. Despite achieving similar calibration metrics, a majority of hydrologic projections of average annual streamflow during the 2080s were statistically different, with differences in magnitude and direction (increase or decrease) compared to historical annual streamflows. At the average monthly time-scale, a majority of the hydrologic projections varied in peak streamflow timing, peak streamflow magnitude, summer streamflows, as well as overall increases or decreases compared to the historical monthly streamflows. Snowmelt projections from the SWAT model also widely varied, both in depth and snowmelt peak timing, for all watersheds. Since a large portion of the runoff-producing regions in the western United States is snowmelt-dependent, this has large implications for the prediction of the amount and timing of streamflow in the coming century. This paper shows that hydrologic model parameterizations that give similar adequate calibration metrics can lead to statistically significant differences in hydrologic projections under climate change. Therefore, researchers and water resource managers should account for this uncertainty by assembling ensemble projections from both multiple parameter sets and GCMs.

A Brief History of Evaluations Performed on the Operational Kings River Winter Orographic Cloud Seeding Program

Abstract: An operational winter orographic cloud seeding program has been conducted in the Kings River Drainage located in the southern Sierra Nevada Mountains of California most winter seasons since water year 1955. Both ground based and airborne seeding modes have been used to disperse silver iodide into naturally occurring winter storms. Several evaluations have been performed to estimate the effectiveness of this seeding program. These evaluations have considered different seeded time periods dependent upon when the evaluation work was published. Since the program has not been randomized, these evaluations have all been based upon the historical target/control technique. Most of these evaluations have used annual streamflow as the response variable. One recent analysis was based upon April 1st snow water content. Control sites were selected from the Yosemite National Park region, an unseeded area, and southern Sierra Nevada sites located south of the Kings River Drainage. Linear regression equations were developed relating the control and target areas annual streamflow values during historical periods without any seeding. High correlations were obtained with r2 values ranging from 0.90 to 0.98. Both linear and multi-linear equations were developed for April 1st snow water contents. High correlations were obtained with r2 values ranging from 0.91 to 0.93. When these equations were used to predict the amount of natural streamflow or snow water contents during seeded years and then compared to the observed values during the seeded years, the average estimated increases in annual streamflow ranged from +3.3 to +6.1%. Similarly, the estimated increases in April 1st snow water content ranged from +4.9% (linear regression) to +5.7% (multi-linear regression).

Symposium 9: Rocky Mountain Futures: Preserving, Utilizing, and Sustaining Rocky Mountain Ecosystems

Symposium 9: Rocky Mountain Futures: Preserving, Utilizing, and Sustaining Rocky Mountain Ecosystems

Eco-Hydrological Requirements in Arid and Semiarid Regions: Case Study of the Yellow River in China

AbstractThe eco-hydrological requirements of a river are related to the health of the river. In recent years, changing climate and intensifying human activities have further aggravated water problems in the Yellow River. Considering hydrological changes, this study addressed the ecological water requirements of the Yellow River basin, wherein the threshold ecological water requirement corresponded to the streamflow with the largest occurrence probability determined by the Pearson Type III distribution. Instream flow ± one standard deviation was adopted as the water resource management target and abrupt changes in streamflow were detected by using the Mann-Whitney U test. The results of the analysis indicated that: (1) the annual flow of the Yellow River substantially decreased after abrupt changes and the probability significantly dropped that the amount of annual streamflow satisfied the ecological instream flow requirement; and (2) the water resource management target was satisfied well after th echange...

Identifying controls of the rainfall–runoff response of small catchments in the tropical Andes (Ecuador)

Summary Tropical mountain regions are characterized by strong spatial climate gradients which together with the limited amount of data and knowledge of the underlying processes hinder the management of the water resources. Especially for regional-scale prediction it is important to identify the dominant factors controlling the rainfall–runoff response and link those to known spatial patterns of climate, soils, and vegetation. This study analyzes the rainfall–runoff relation of 13 intensively monitored micro-catchments in the Andes of southern Ecuador. The results of this study show that streamflow in the southern cordillera of the Ecuadorian Andes, above 2500 m a.s.l., primarily consists of subsurface flow. The yearly amount of streamflow is controlled by the annual rainfall depth, whereas the temporal distribution is mainly governed by the lateral saturated hydraulic conductivity, the soil water retention and the antecedent soil moisture content. Anthropogenic effects were found insignificant, with the exception in one of the studied micro-catchment. Effect of land use changes in most of the micro-catchments did not reflect in the shape of the flow duration curve because either the spatial extent of human impact was small and/or the overall basin slope was less than 20%.

Hydrological characteristics of the Rongbuk Glacier catchment in Mt. Qomolangma region in the central Himalayas, China

From 8 April to 11 October in 2005, hydrological observation of the Rongbuk Glacier catchment was carried out in the Mt. Qomolangma (Everest) region in the central Himalayas, China. The results demonstrated that due to its large area with glacier lakes at the tongue of the Rongbuk Glacier, a large amount of stream flow was found at night, which indicates the strong storage characteristic of the Rongbuk Glacier catchment. There was a time lag ranging from 8 to 14 hours between daily discharge peaks and maximum melting (maximum temperature). As melting went on the time lag got shorter. A high correlation was found between the hydrological process and daily temperature during the ablation period. The runoff from April to October was about 80% of the total in the observation period. Compared with the discharge data in 1959, the runoff in 2005 was much more, and the runoff in June, July and August increased by 69%, 35% and 14%, respectively. The rising of temperature is a major factor causing the increase in runoff. The discharges from precipitation and snow and ice melting are separated. The discharge induced by precipitation accounts for about 20% of the total runoff, while snow and ice melting for about 80%.

Simulated soil water storage effects on streamflow generation in a mountainous snowmelt environment, Idaho, USA

AbstractAlthough soil processes affect the timing and amount of streamflow generated from snowmelt, they are often overlooked in estimations of snowmelt‐generated streamflow in the western USA. The use of a soil water balance modelling approach to incorporate the effects of soil processes, in particular soil water storage, on the timing and amount of snowmelt generated streamflow, was investigated. The study was conducted in the Reynolds Mountain East (RME) watershed, a 38 ha, snowmelt‐dominated watershed in southwest Idaho. Snowmelt or rainfall inputs to the soil were determined using a well established snow accumulation and melt model (Isnobal). The soil water balance model was first evaluated at a point scale, using periodic soil water content measurements made over two years at 14 sites. In general, the simulated soil water profiles were in agreement with measurements (P < 0·05) as further indicated by high R2 values (mostly > 0·85), y‐intercept values near 0, slopes near 1 and low average differences between measured and modelled values. In addition, observed soil water dynamics were generally consistent with critical model assumptions. Spatially distributed simulations over the watershed for the same two years indicate that streamflow initiation and cessation are closely linked to the overall watershed soil water storage capacity, which acts as a threshold. When soil water storage was below the threshold, streamflow was insensitive to snowmelt inputs, but once the threshold was crossed, the streamflow response was very rapid. At these times there was a relatively high degree of spatial continuity of satiated soils within the watershed. Incorporation of soil water storage effects may improve estimation of the timing and amount of streamflow generated from mountainous watersheds dominated by snowmelt. Copyright © 2008 John Wiley & Sons, Ltd.