Melted snow volume control in the snowmelt runoff model using a snow water equivalent statistically based model

Snowmelt is an important component of the river discharge in mountain environments. In the past 40 years, the snowmelt dynamics has been mostly evaluated using degree‐day‐based models like the snowmelt runoff model (SRM). This model has no control on the volume of the melting snow, even if SRM includes as data input the snow‐covered area. This lack explains why the application of SRM may lead to inaccurate snowmelt volume estimations, even if the discharge volumes are accurately reproduced. Here we introduce in SRM the control on the melted snow volume and consider it in the determination of SRM parameters. The total snow volume, accumulated at the end of winter season, is evaluated by a snow water equivalent statistically based model, SWE‐SEM, and used as an estimate of the melting snow during the summer season. The benefit derived from the introduction of the control on the melting snow volume was investigated in the Mallero basin (northern Italy) for the 2003 and 2004 snow melting seasons. The analysis compares the model's results adopting different parameter sets, both considering and ignoring the control on the melting snow volume. Copyright © 2011 John Wiley & Sons, Ltd.     

Estimating source regions for snowmelt runoff in a Rocky Mountain basin: tests of a data‐based conceptual modeling approach

In many mountain basins, river discharge measurements are located far away from runoff source areas. This study tests whether a basic snowmelt runoff conceptual model can be used to estimate relative contributions of different elevation zones to basin‐scale discharge in the Cache la Poudre, a snowmelt‐dominated Rocky Mountain river. Model tests evaluate scenarios that vary model configuration, input variables, and parameter values to determine how these factors affect discharge simulation and the distribution of runoff generation with elevation. Results show that the model simulates basin discharge well (NSCE and R >0.90) when input precipitation and temperature are distributed with different lapse rates, with a rain‐snow threshold parameter between 0 and 3.3 °C, and with a melt rate parameter between 2 and 4 mm °C^?1 d^?1 because these variables and parameters can have compensating interactions with each other and with the runoff coefficient parameter. Only the hydrograph recession parameter can be uniquely defined with this model structure. These non‐unique model scenarios with different configurations, input variables, and parameter values all indicate that the majority of basin discharge comes from elevations above 2900 m, or less than 25% of the basin total area, with a steep increase in runoff generation above 2600 m. However, the simulations produce unrealistically low runoff ratios for elevations above 3000 m, highlighting the need for additional measurements of snow and discharge at under‐sampled elevations to evaluate the accuracy of simulated snow and runoff patterns. Copyright © 2013 John Wiley & Sons, Ltd.     

Water isotopes and hydrograph separation in different glacial catchments in the southeast margin of the Tibetan Plateau

Snow and glaciers are known to be important sources for freshwater; nevertheless, our understanding of the hydrological functioning of glacial catchments remains limited when compared with lower altitude catchments. In this study, a temperate glacial region located in the southeast margin of the Tibetan Plateau is selected to analyse the characteristics of δ¹⁸O and δD in different water sources and the contribution of glacier–snow meltwater to streamflow. The results indicate that the δ¹⁸O of river water ranges from ?16.2‰ to ?10.2‰ with a mean of ?14.1‰ and that the δD values range from ?117.0‰ to ?68.0‰ with a mean of ?103.1‰. These values are more negative than those of glacier–snow meltwater but less negative than those of precipitation. The d ‐excess values are found to decrease from meltwater to river to lake/reservoir water as a result of evaporation. On the basis of hydrograph separation, glacier–snow meltwater accounts for 51.5% of river water in the Baishui catchment in the melting season. In the Yanggong catchment, snow meltwater contributes 47.9% to river water in the premonsoon period, and glacier meltwater contributes only 6.8% in the monsoon period. The uncertainty in hydrograph separation is sensitive to the variation of tracer concentrations of streamflow components. The input of meltwater to a water system varies with local climate and glacier changes. The results confirm that hydrograph separation using water isotopes is valuable for evaluating the recharge sources of rivers, especially in ungauged glacial regions. This study provides insights into the hydrological processes of glacial catchments on the Tibetan Plateau, which is important for water resource management.     

Climate variability,snow, and physiographic controls on storm hydrographs in small forested basins,western Cascades,Oregon

Large floods are often attributed to the melting of snow during a rain event. This study tested how climate variability, snowpack presence, and basin physiography were related to storm hydrograph shape in three small (<1 km²) basins with old‐growth forest in western Oregon. Relationships between hydrograph characteristics and precipitation were tested for approximately 800 storms over a nearly 30‐year period. Analyses controlled for (1) snowpack presence/absence, (2) antecedent soil moisture, and (3) hillslope length and gradient. For small storms (<150 mm precipitation), controlling for precipitation, the presence of a snowpack on near‐saturated soil increased the threshold of precipitation before hydrograph rise, extended the start lag, centroid lag, and duration of storm hydrographs, and increased the peak discharge. The presence of a snowpack on near‐saturated soil sped up and steepened storm hydrographs in a basin with short steep slopes, but delayed storm hydrographs in basins with longer or more gentle slopes. Hydrographs of the largest events, which were extreme regional rain and rain‐on‐snow floods, were not sensitive to landform characteristics or snowpack presence/absence. Although the presence of a snowpack did not increase peak discharge in small, forested basins during large storms, it had contrasting effects on storm timing in small basins, potentially synchronizing small basin contributions to the larger basin hydrograph during large rain‐on‐snow events. By altering the relative timing of hydrographs, snowpack melting could produce extreme floods from precipitation events whose size is not extreme. Further work is needed to examine effects of canopy openings, snowpack, and climate warming on extreme rain‐on‐snow floods at the large basin scale. Copyright © 2008 John Wiley & Sons, Ltd.     

Hydrograph separation and precipitation source identification using stable water isotopes and conductivity: River Ganga at Himalayan foothills

The observed retreat of several Himalayan glaciers and snow packs is a cause of concern for the huge population in southern Asia that is dependent on the glacial‐fed rivers emanating from Himalayas. There is considerable uncertainty about how cryospheric recession in the Himalayan region will respond to climate change, and how the water resource availability will be affected. As a first step towards quantifying the contribution of glacier‐melt water, hydrograph separation of River Ganga at Rishikesh into its constituent components, namely (i) surface runoff, (ii) glacial ice‐melt and (iii) groundwater discharge has been done in this paper. A three‐component mixing model has been employed using the values of δ¹⁸O and electrical conductivity (EC) of the river water, and its constituents, to estimate the time‐varying relative fraction of each component. The relative fraction of the surface runoff peaks (70–90%) during winter, due to the near‐zero contribution of glacial ice‐melt, essentially represents the melting of surface snow from the catchment. The contribution of glacial ice‐melt to the stream discharge peaks during summer and monsoon reaches a maximum value of ～40% with an average of 32%. The fraction of groundwater discharge varies within a narrow range (15 ± 5%) throughout the year. On the basis of the variation in the d‐excess values of river water, it is also suggested that the snow‐melt and ice‐melt component has a significant fraction derived from winter precipitation with moisture source from mid‐latitude westerlies (also known as western disturbances). Copyright © 2010 John Wiley & Sons, Ltd.     

Arctic Climate and Water Change: Model and Observation Relevance for Assessment and Adaptation

The Arctic is subject to growing economic and political interest. Meanwhile, its climate and water systems are in rapid transformation. In this paper, we review and extend a set of studies on climate model results, hydro-climatic change, and hydrological monitoring systems. Results indicate that general circulation model (GCM) projections of drainage basin temperature and precipitation have improved between two model generations. However, some inaccuracies remain for precipitation projections. When considering geographical priorities for monitoring or adaptation efforts, our results indicate that future projections by GCMs and recent observations diverge regarding the basins where temperature and precipitation changes currently are the most pronounced and where they will be so in the future. Regarding late twentieth-century discharge changes in major Arctic rivers, data generally show excess of water relative to precipitation changes. This indicates a possible contribution to sea-level rise of river water that was previously stored in permafrost or groundwater. The river contribution to the increasing Arctic Ocean freshwater inflow is similar in magnitude to the separate contribution from glaciers, which underlines the importance of considering all possible sources of freshwater when assessing sea-level change. We further investigate monitoring systems and find a lack of harmonized water chemistry data, which limits the ability to understand the origin and transport of nutrients, carbon and sediment to the sea. To provide adequate information for research and policy, Arctic hydrological and hydrochemical monitoring needs to be extended, better integrated and made more accessible. Further water-focused data and modeling efforts are required to resolve the source of excess discharge in Arctic rivers. Finally, improvements in climate model parameterizations are needed, in particular for precipitation projections.     

Relative importance of snow accumulation and monsoon rainfall data for estimating annual runoff,Jhelum basin,Pakistan

Abstract

The relative importance of data on winter snow accumulation and summer (monsoon) rainfall for estimating annual runoff in the Jhelum River basin, Punjab Himalaya, Pakistan, has been investigated. Strong correlations were found between point measurements of the annual maximum of snowpack water equivalent and of total winter precipitation in the Kunhar sub-basin, and total annual discharge. In addition, total winter snowfall showed a generally significant correlation with annual discharge. Elevation did not appear to play a strong role in determining the usefulness of these measurements, whereas location within the basin relative to large scale precipitation patterns did, in some cases. Monsoon rainfall appeared to be a very poor indicator of annual discharge. The results also suggest that the operation of a continental scale negative feedback mechanism between Eurasian snow cover and the Indian monsoon might be felt in this region of the Himalaya.     

On the Use of Hydrological Models and Satellite Data to Study the Water Budget of River Basins Affected by Human Activities: Examples from the Garonne Basin of France

Natural and anthropogenic forcing factors and their changes significantly impact water resources in many river basins around the world. Information on such changes can be derived from fine scale in situ and satellite observations, used in combination with hydrological models. The latter need to account for hydrological changes caused by human activities to correctly estimate the actual water resource. In this study, we consider the catchment area of the Garonne river (in France) to investigate the capabilities of space-based observations and up-to-date hydrological modeling in estimating water resources of a river basin modified by human activities and a changing climate. Using the ISBA–MODCOU and SWAT hydrological models, we find that the water resources of the Garonne basin display a negative climate trend since 1960. The snow component of the two models is validated using the moderate-resolution imaging spectroradiometer snow cover extent climatology. Crop sowing dates based on remote sensing studies are also considered in the validation procedure. Use of this dataset improves the simulated evapotranspiration and river discharge amounts when compared to conventional data. Finally, we investigate the benefit of using the MAELIA multi-agent model that accounts for a realistic agricultural and management scenario. Among other results, we find that changes in crop systems have significant impacts on water uptake for agriculture. This work constitutes a basis for the construction of a future modeling framework of the sociological and hydrological system of the Garonne river region.     

ISOTOPIC AND IONIC VARIATIONS IN GLACIER RIVER WATER DURING THREE CONTRASTING ABLATION SEASONS

The significance of the baseflow component of glacier river discharge in summer varies with geographical location, altitude, glacier geometry and glacier size. Baseflow is maintained by meltwater generated above the transient equilibrium line and by water released from temporary storage on, in or beneath the glacier. At the Norwegian glacier Austre Okstindbreen, where precipitation is generally high throughout the year and the summers are cool and wet, observations in three successive, but contrasting, years have shown that Na⁺ ion concentrations in the glacier river water are influenced strongly by the amount of snowmelt. This itself depends on the preceding winter conditions, which determine the amount of accumulation, and on the current summer's weather. The efficiency of the glacier's drainage systems depends on the general progress of summer ablation. The speed with which the systems develop influences ion provision from subglacial sources. Ca²⁺ ion concentrations are largely determined by subglacial conditions. Oxygen isotope variations in glacier river water reflect the relative contributions made to total discharge by snow meltwater and other sources; the composition of the snow cover, which is a function of winter temperatures, has a strong influence. Ice meltwater has low isotopic variability, but the isotopic composition of rainfall varies markedly. A simple model of mixing of englacial and subglacial waters, each of a constant composition, cannot be applied to a high-latitude glacier of the size and altitudinal range of Austre Okstindbreen.     

Water temperature dynamics in High Arctic river basins

Despite the high sensitivity of polar regions to climate change and the strong influence of temperature upon ecosystem processes, contemporary understanding of water temperature dynamics in Arctic river systems is limited. This research gap was addressed by exploring high‐resolution water column thermal regimes for glacier‐fed and non‐glacial rivers at eight sites across Svalbard during the 2010 melt season. Mean water column temperatures in glacier‐fed rivers (0.3–3.2 °C) were lowest and least variable near the glacier terminus but increased downstream (0.7–2.3 °C km^–1). Non‐glacial rivers, where discharge was sourced primarily from snowmelt runoff, were warmer (mean: 2.9–5.7 °C) and more variable, indicating increased water residence times in shallow alluvial zones and increased potential for atmospheric influence. Mean summer water temperature and the magnitude of daily thermal variation were similar to those of some Alaskan Arctic rivers but low at all sites when compared with alpine glacierized environments at lower latitudes. Thermal regimes were correlated strongly (p < 0.01) with incoming short‐wave radiation, air temperature, and river discharge. Principal drivers of thermal variability were inferred to be (i) water source (i.e. glacier melt, snowmelt, groundwater); (ii) exposure time to the atmosphere; (iii) prevailing meteorological conditions; (iv) river discharge; (v) runoff interaction with permafrost and buried ice; and (vi) basin‐specific geomorphological features (e.g. channel morphology). These results provide insight into the potential changes in high‐latitude river systems in the context of projected warming in polar regions. We hypothesize that warmer and more variable temperature regimes may prevail in the future as the proportion of bulk discharge sourced from glacial meltwater declines and rivers undergo a progressive shift towards snow water and groundwater sources. Importantly, such changes could have implications for aquatic species diversity and abundance and influence rates of ecosystem functioning in high‐latitude river systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Thermal and isotopic evidence for surface and subsurface water contributions to baseflow in a high Arctic river

Seven longitudinal water temperature tow surveys were conducted to attempt to identify the location of surface and subsurface river water exchanges along the length of the West River at the Cape Bounty Arctic Watershed Observatory, Melville Island, Nunavut, Canada (74°55′ N, 109°35′ W). Water temperature data were collected using a calibrated thermistor with an accuracy of ±0.002 °C (resolution <0.00005 °C) along the river during July 2014 in conjunction with stable water isotope sampling to support the thermal data and to determine the extent of surface water mixing from different sources such as precipitation, snowmelt, and surface/subsurface water contributions to the river. Atmospheric conditions were found to be the main contributor to seasonal temperature variance in the river, whereas tributary inflows and residual channel snow also had important thermal effects to river temperatures. Residual channel snow was a sustained source of cold water during much of the 2014 summer season (June–August) and substantially offset downstream warming. The longitudinal temperature profiles indicate notable changes to the thermal state of the river, which are interpreted to be indicative of subsurface and surface water exchange through inputs of relatively cold or warm water. Broadly, surface inflows were found to provide warmer water relative to the West River, and contributed to downstream warming of the river, along with downstream enrichment of δD and δ¹⁸O. Subsurface inflows provided cooler water relative to the river, and contributed to downstream depletion of δD and δ¹⁸O and downstream cooling of river temperatures. These results demonstrate that localized changes in river temperature, in conjunction with isotopic tracers, can be used to track channel–slope water interactions in Arctic hydrological systems, work previously limited to alpine and temperate settings.     

Modeling the effects of climate change projections on streamflow in the Nooksack River basin,Northwest Washington

The Nooksack River has its headwaters in the North Cascade Mountains and drains an approximately 2000 km² watershed in northwestern Washington State. The timing and magnitude of streamflow in a snowpack‐dominated drainage basin such as the Nooksack River basin are strongly influenced by temperature and precipitation. Projections of future climate made by general circulation models (GCMs) indicate increases in temperature and variable changes in precipitation for the Nooksack River basin. Understanding the response of the river to climate change is crucial for regional water resources planning because municipalities, tribes, and industry depend on the river for water use and for fish habitat. We combine three different climate scenarios downscaled from GCMs and the Distributed‐Hydrology‐Soil‐Vegetation Model to simulate future changes to timing and magnitude of streamflow in the higher elevations of the Nooksack River. Simulations of future streamflow and snowpack in the basin project a range of magnitudes, which reflects the variable meteorological changes indicated by the three GCM scenarios and the local natural variability employed in the modeling. Simulation results project increased winter flows, decreased summer flows, decreased snowpack, and a shift in timing of the spring melt peak and maximum snow water equivalent. These results are consistent with previous regional studies, but the magnitude of increased winter flows and total annual runoff is higher. Increases in temperature dominate snowpack declines and changes to spring and summer streamflow, whereas a combination of increases in temperature and precipitation control increased winter streamflow. Copyright © 2013 John Wiley & Sons, Ltd.     

Estimating the effects of climate change on the intensification of monsoonal‐driven stream discharge in a Himalayan watershed

Understanding potential hydrologic influences to continued climate change in Himalayan watersheds is important for management of transnational water resources. This study estimates the climate change impacts on hydrologic processes of the Kali Gandaki watershed from central Himalayan region using the Soil and Water Assessment Tool. Daily predicted stream discharge of the basin for 1981–95 following calibration was accurate with Nash Sutcliffe Efficiency value >0.75. Sensitivity analysis of the hydrologic parameters showed the precipitation and temperature lapse rates as the most sensitive parameters to the stream discharge. To assess the influence of continued climate change on hydrologic processes, we modified the weather inputs for the model using average, minimum and maximum temperature, and precipitation changes for the Special Report on Emission Scenarios B1, A1B and A2 derived from 16 General Circulation Models for 2080s. Mean annual stream discharge was approximately 39% higher than current values for the maximum temperature and precipitation changes of the A2 scenario and 22% less for minimum changes of the same scenario. Stream discharge was projected to be changed by +9% during monsoon season and by ?6% during pre‐monsoon season. Snowfall and snow melt were projected to be 30% and 29%, respectively, less than the current average for the maximum temperature and precipitation changes of the A2 scenario. Future simulations showed potential increase in monsoonal stream discharge associated with projected higher precipitation which when coupled with enhanced summer glacier melt might influence the downstream water availability of the basin. Copyright © 2013 John Wiley & Sons, Ltd.     

Climate changes and their impacts on water resources in the arid regions: a case study of the Tarim River basin, China

Streamflow series of five hydrological stations were analyzed with aim to indicate variability of water resources in the Tarim River basin. Besides, impacts of climate changes on water resources were investigated by analyzing daily precipitation and temperature data of 23 meteorological stations covering 1960–2005. Some interesting and important results were obtained: (1) the study region is characterized by increasing temperature, however, only temperature in autumn is in significant increasing trend; (2) precipitation changes present different properties. Generally, increasing precipitation can be detected. However, only the precipitation in the Tienshan mountain area is in significant increasing trend. Annual streamflow of major rivers of the Tarim River basin are not in significant trends, except that of the Akesu River which is in significantly increasing trend. Due to the geomorphologic properties of the Tienshan mountain area, precipitation in this area demonstrates significant increasing trend and which in turn leads to increasing streamflow of the Akesu River. Due to the fact that the sources of streamflow of the rivers in the Tarim River basin are precipitation and melting glacial, both increasing precipitation and accelerating melting ice has the potential to cause increasing streamflow. These results are of practical and scientific merits in basin-scale water resource management in the arid regions in China under the changing environment.     

Hydrological dynamics of snowmelt induced streamflow in a high mountain catchment of the Pyrenees under contrasting snow accumulation and duration years

Snowmelt drives a large portion of streamflow in many mountain areas of the world. However, the water paths from snowmelt to the arrival of the water in the streams are still largely unknown. This work analyzes for first time the influence of snowmelt on spring streamflow with different snow accumulation and duration, in an alpine catchment of the central Spanish Pyrenees. This study presents the water balance of the main melting months (May and June). Piezometric values, water temperature, electrical conductivity and isotope data (δ¹⁸O) allow a better understanding of the hydrological functioning of the basin during these months. Results of the water balance calculations showed that snow represented on average 73% of the water available for streamflow in May and June while precipitation during these months accounted for only 27%. However, rainfall during the melting period was important to determine the shape of the spring hydrographs. On average, 78% of the sum of both the snow water equivalent (SWE) accumulated at the beginning of May and the precipitation in May and June converted into runoff during the May–June melting period. The average evaporation-sublimation during the 2 months corresponded to 8.4% of the accumulated SWE and rainfall, so that only a small part of the water input was ultimately available for soil and groundwater storage. When snow cover disappeared from the catchment, soil water storage and streamflow showed a sharp decline. Consequently, streamflow electrical conductivity, temperature and δ¹⁸O showed a marked tipping point towards higher values. The fast hydrological response of the catchment to snow and meteorological fluctuations, as well as the marked diel fluctuations of streamflow δ¹⁸O during the melting period, strongly suggests short meltwater transit times. As a consequence of this hydrological behaviour, independently of the amount of snow accumulated and of melting date, summer streamflow remained always low, with only small runoff peaks driven by rainfall events.     

On the usefulness of remote sensing input data for spatially distributed hydrological modelling: case of the Tarim River basin in China

The ecological situation of the Tarim River basin in China seriously declined since the early 1950s, mainly due to a strong increase in water abstraction for irrigation purposes. To restore the ecological system and support sustainable development of the Tarim River basin region in China, more hydrological studies are demanded to properly understand the processes of the watershed and efficiently manage the water resources. Such studies are, however, complicated due to the limited data availability, especially in the mountainous headwater regions of the Tarim River basin. This study investigated the usefulness of remote sensing (RS) data to overcome that lack of data in the spatially distributed hydrological modelling of the basin. Complementary to the conventional station‐based (SB) data, the RS products that are directly used in this study include precipitation, evapotranspiration and leaf area index. They are derived from raw image data of the Chinese Fengyun meteorological satellite and from the Moderate Resolution Imaging Spectroradiometer (MODIS). The MODIS land surface temperature was used to calculate the atmospheric temperature lapse rate to describe the temperature dependency on topographical variations. Moreover, MODIS‐based snow cover images were used to obtain model initial conditions and as validation reference for the snow model component. Comparison of model results based on RS input versus conventional SB input exhibited similar results in terms of high and low river runoff extremes, cumulative runoff volumes in both runoff and snow melting seasons and spatial and temporal variability of snow cover. During summer time, when the snow cover shrinks in the permanent glacier region, it was found that the model resolution influences the model results dramatically, hence, showing the importance of detailed (RS based) spatially distributed input data. Copyright © 2011 John Wiley & Sons, Ltd.     

Spatiotemporal dynamics of water sources in a mountain river basin inferred through δ2H and δ18O of water

In mountainous river basins of the Pacific Northwest, climate models predict that winter warming will result in increased precipitation falling as rain and decreased snowpack. A detailed understanding of the spatial and temporal dynamics of water sources across river networks will help illuminate climate change impacts on river flow regimes. Because the stable isotopic composition of precipitation varies geographically, variation in surface water isotope ratios indicates the volume-weighted integration of upstream source water. We measured the stable isotope ratios of surface water samples collected in the Snoqualmie River basin in western Washington over June and September 2017 and the 2018 water year. We used ordinary least squares regression and geostatistical Spatial Stream Network models to relate surface water isotope ratios to mean watershed elevation (MWE) across seasons. Geologic and discharge data was integrated with water isotopes to create a conceptual model of streamflow generation for the Snoqualmie River. We found that surface water stable isotope ratios were lowest in the spring and highest in the dry, Mediterranean summer, but related strongly to MWE throughout the year. Low isotope ratios in spring reflect the input of snowmelt into high elevation tributaries. High summer isotope ratios suggest that groundwater is sourced from low elevation areas and recharged by winter precipitation. Overall, our results suggest that baseflow in the Snoqualmie River may be relatively resilient to predicted warming and subsequent changes to snowpack in the Pacific Northwest.     

On the hydrological difference between catchments above and below the intermittent-persistent snow transition

Because of the importance of snow for river discharge in mountain regions, hydrological research often focuses on seasonally snow-covered zones. However, in many basins the majority of the land surface area is intermittently snow-covered. Discharge monitoring in these areas is less common, so their contributions to downstream rivers remain largely unknown. We evaluated hydrological differences between three intermittently snow-covered (mean annual Jan 1–Jul 3 snow persistence <60%) and two seasonally snow-covered headwater catchments in the Colorado Front Range. We compared water balance variables to evaluate how and why discharge differs between the snow zones and estimated the relative contributions from each snow zone to regional river discharge. We focused on water years 2016–2019 and used a combination of in situ sensors and regional climate datasets. Annual discharge from the intermittent snow zone was low for all three catchments (10–77 mm), despite covering a wide range in annual snow persistence (25%–64%), whereas annual discharge from the seasonal snow zone was up to 73 times higher. Soil moisture in the seasonal snow zone was above field capacity for longer periods of time than in the intermittent snow zone, and the intermittent snow zone was uniquely subject to soil freezing (up to 102 days per year). For most of the year, potential evapotranspiration exceeded rainfall and snowmelt inputs in the intermittent snow zone, but was lower than rainfall and snowmelt inputs in the seasonal snow zone. This is likely a primary driver of the differences in soil moisture and discharge for catchments with a seasonal versus intermittent snow cover. Despite the large difference in discharge between these two snow zones, the intermittent snow zone contributed about a quarter of the discharge in the regional river, highlighting the importance of studying discharge generation across all elevations.     

Regional water balance modelling in the NOPEX area: development and application of monthly water balance models

One of the main purposes of a water balance study is to evaluate the net available water resources, both on the surface and in the subsurface. Water balance models that simulate hydrographs of river flow on the basis of available meteorological data would be a valuable tool in the hands of the planners and designers of water resources systems. In this paper, a set of simple monthly snow and water balance models has been developed and applied to regional water balance studies in the NOPEX area. The models require as input monthly areal precipitation, monthly long-term average potential evapotranspiration and monthly mean air temperature. The model outputs are monthly river flow and other water balance components, such as actual evapotranspiration, slow and fast components of river flow, snow accumulation and melting. The results suggest that the proposed model structure is suitable for water balance study purposes in seasonally snow-covered catchments located in the region.