No description available.

Glaciated catchments increasingly accommodate rising populations. As glaciers are capable of modifying peak flows and releasing floodwaters, understanding and developing models of subglacial water storage and release has significance to the safety of resident populations and land use decision-making. Glaciological and hydrometeorological processes play a critical role in determining water storage within the subglacial drainage system of Alpine glaciers. However, our understanding of spatial variations of these processes throughout the ablation season remains incomplete. Field results and modelling studies of the glacial hydrological system at Findelengletscher, Canton Valais, Switzerland are presented with a view to improving understanding of physical mechanisms controlling water flow within glacierised catchments. A physically-based model of surface runoff incorporating meltwater and precipitation has been developed. This model has limited data requirements using only air temperature, solar radiation, precipitation and elevation of the transient snow line in a simple, spatially distributed energy balance model. It has been used to predict surface runoff at an hourly resolution for the 1999 ablation season. Methodological advances have been made by creating conceptual models of water flow through the subglacial drainage system. Models are used for semi-quantitative interpretation of water level variations in boreholes, as surrogate measures of subglacial water pressures. The boreholes either directly intersect subglacial channels or hydraulically connect to subglacial channels through a subglacial sediment layer. Variations in borehole water levels are considered at both diurnal and seasonal timescales. Water storage has been calculated within the subglacial drainage network and interpretations are made of temporal variations in subglacial water storage. Borehole water levels indicate that the glacier subsole can be spatially separated into those areas that are hydraulically connected or unconnected to the subglacial drainage system. Hydraulically connected areas may further be subdivided into areas of efficient and inefficient subglacial drainage. These may intermittently connect and influence water balance within a glacier. Increasing and decreasing trends in water balance cycles are initiated by glaciohydrological mechanisms. These control the activity of intermittent hydraulic connections between efficient and inefficient areas of subglacial drainage. Connections form in response to two hydrometeorological factors: high elevation rainfall and short duration decreases in elevation of either the snowline or the 0°C isotherm. Increasing trends in water balance over successive days are associated with preferential routing of inputs into, and retention within, hydraulically inefficient areas of the subglacial drainage system. Occasionally the release of water from temporary subglacial storage is not synchronous with either hydrometeorological causal factor. Measurements of fall-line velocity and vertical displacement suggest that basal sliding may alter preferential subglacial flow pathways. However, uncertainty exists as to whether such changes may be the result of lagged effects of either high water pressures from rainfall or low water pressures from low daily surface runoff. These uncertainties are due to system response times affecting the time taken to transfer longitudinal strain within glacier ice. In the late ablation season the potential for rapid surface runoff over the annual maximum snowfree area within the catchment is high. In the event of a large rainfall event the capacity of a tunnel-conduit system to discharge may have decreased sufficiently to cause temporary retention of a large proportion of surface runoff, predominantly within distributed drainage. Temporary storage followed by re-integration of hydraulic connections formed earlier in the ablation season, increases the potential for proportionally large discharge events (relative to the volumes of inputs) in the late ablation season. Flooding in glacierised basins becomes more likely as a result.

Understanding the controls on water movement on forested uplands is critical in predicting the potential effects of disturbance on the sustainability of water resources. I examined the controls on vertical and lateral water movement on forested uplands on a range of landforms (coarse textured outwash, fine textured moraine) and time periods (individual events, during snowmelt, through the growing season, annually, and long-term) at the Utikuma Region Study Area (URSA) on the sub-humid Boreal Plains of Alberta, Canada. To quantify vertical and lateral water movement, hydrometric and tracer measurements were made under natural and experimental conditions at plot and hillslope scales. Vertical flow and unsaturated zone storage dominated hydrologic response to snowmelt and rainfall at the plot and hillslope scales. Plot-scale snowmelt infiltration was greater than near-surface runoff, and when runoff occurred it was limited to south-facing outwash hillslopes underlain by concrete frost. Rainfall simulation studies showed that even under the extreme conditions tested, vertical flow and storage dominated the hydrologic response. Soils at field capacity and precipitation inputs of 15-20 mm or greater at high intensities were required to generate lateral flow via the transmissivity feedback mechanism. The threshold soil moisture and precipitation conditions are such that lateral flow will occur infrequently under natural conditions. Seasonal vertical water movement under natural conditions was greater on outwash than moraine uplands. The maximum downward vertical movement occurred in response to snowmelt, with little subsequent movement over the growing season. Recharge following snowmelt was similar for outwash and moraine sites and was followed by declining water tables through the growing season. Tracer estimates of long-term root zone drainage were low, while estimates of recharge for the moraine were high, raising questions about the appropriateness of this method for these sites. These results emphasize the dominance of vertical relative to lateral water flow on Boreal Plain uplands. Detailed understanding of the controls on water movement can be used to predict the potential effects of disturbance on hydrology and water resources. / Ecology

Accurate knowledge of water content in seasonal snow can be helpful for water resource management. In this study, a distributed temperature index snow model based on temperature and precipitation as forcing data, is used to estimate snow storage in the Jollie catchment approximately 20km east of the main divide of the central Southern Alps, New Zealand. The main objective is to apply a frequently used assimilation method, the ensemble Kalman square root filter, to assimilate remotely sensed snow covered area into the model and evaluate the impacts of this approach on simulations of snow water equivalent. A 250m resolution remotely sensed data from Moderate Resolution Imaging Spectroradiometer (MODIS), specifically tuned to the study location was used. Temperature and precipitation were given on a 0.055 latitude/longitude grid. Precipitation was perturbed as input into the model, generating 100 ensemble members, which represented model error. Only observations of snow covered area that had less that 25% cloud cover classification were used in the assimilation precess. The error in the snow covered area observations was assumed to be 0.1 and grow linearly with cloud cover fraction up to 1 for a totally cloud covered pixel. As the model was not calibrated, two withholding experiments were conducted, in which observations withheld from the assimilation process were compared to the results. Two model states were updated in the assimilation, the total snow accumulation state variable and the total snow melt state variable. The results of this study indicate that the model underestimates snow storage at the end of winter and/or does not detect snow fall events during the ablation period. The assimilation method only affected simulated snow covered area and snow storage during the ablation period. That corresponded to higher correlation between modelled snow cover area and the updated state variables. Withholding experiments show good agreement between observations and simulated snow covered area. This study successfully applied the ensemble Kalman square root filter and showed its applicability for New Zealand conditions.

Accurate knowledge of water content in seasonal snow can be helpful for water resource management. In this study, a distributed temperature index snow model based on temperature and precipitation as forcing data, is used to estimate snow storage in the Jollie catchment approximately 20km east of the main divide of the central Southern Alps, New Zealand. The main objective is to apply a frequently used assimilation method, the ensemble Kalman square root filter, to assimilate remotely sensed snow covered area into the model and evaluate the impacts of this approach on simulations of snow water equivalent. A 250m resolution remotely sensed data from Moderate Resolution Imaging Spectroradiometer (MODIS), specifically tuned to the study location was used. Temperature and precipitation were given on a 0.055 latitude/longitude grid. Precipitation was perturbed as input into the model, generating 100 ensemble members, which represented model error. Only observations of snow covered area that had less that 25% cloud cover classification were used in the assimilation precess. The error in the snow covered area observations was assumed to be 0.1 and grow linearly with cloud cover fraction up to 1 for a totally cloud covered pixel. As the model was not calibrated, two withholding experiments were conducted, in which observations withheld from the assimilation process were compared to the results. Two model states were updated in the assimilation, the total snow accumulation state variable and the total snow melt state variable. The results of this study indicate that the model underestimates snow storage at the end of winter and/or does not detect snow fall events during the ablation period. The assimilation method only affected simulated snow covered area and snow storage during the ablation period. That corresponded to higher correlation between modelled snow cover area and the updated state variables. Withholding experiments show good agreement between observations and simulated snow covered area. This study successfully applied the ensemble Kalman square root filter and showed its applicability for New Zealand conditions.

No description available.

Vattenkraft är en stor källa till energi i Sverige, främst i de norra delarna av landet. För att få ut maximal potential från vattenkraftverken behövs information om hur mycket vatten eller snö det finns uppströms från kraftverken. Genom att få fram tillförlitliga värden av snömängd är det möjligt att minska osäkerheten i uppskattningarna.Eftersom det är svårt att kartera större avrinningsområden via markbundna observationer, både praktiskt och ekonomiskt, har drönarobservationer utvecklats. För att använda sig av drönare krävs det vetskap om var de ska flygas i för område för att hela avrinningsområdet ska representeras. I projektet tas en modell fram i ArcGIS för att hitta mindre områden inom avrinningsområden som ska vara representativa inom utvalda parametrar. I projektet berörs parametrarna vegetation, höjd, lutningsgrad samt dess riktning.Arbetet för att ta fram en modell som ska underlätta framtida arbete inom och utanför forskningsprojektet DRONES är uppdelat i två delar. Den första delen är att ta fram och granska vilka parametrar som påverkar snödjupet i avrinningsområdet. Den andra delen innefattar arbetet med att skapa en modell i ArcGIS som ska analysera ett avrinningsområde med framtagna parametrar för att hitta mindre områden som representerar det hela.Resultatet från de framtagna modellerna kan tillämpas för att underlätta kartläggningen och snödjupsmätningar i avrinningsområden, vilket kan utnyttjas vid effektivisering av vattenreglering. / Hydropower is a major source of energy in Sweden mainly in the northern parts of the country. To get the maximum potential from the hydropower plants, information is required on how much water or snow there is upstream from the power plants. By obtaining reliable values of the amount of snow, it is possible to reduce the uncertainty in forecasts on spring flood.Due to difficulties in mapping larger catchment areas via ground-level observations, drone observations have been developed. In order to use drone observations, knowledge of where they are to be flown to represent the entire catchment area is required. In this project, a model was developed in ArcGIS to find smaller areas within catchments that are to be representative within selected parameters. The project touches upon the parameters vegetation, height, slope and aspect.The work to develop a model that will facilitate future work within and outside the DRONES research project is divided into two parts. The first part is to analyze which parameters affect the snow depth in the catchment area. The second part consists of creating a model in ArcGIS that will find a smaller area inside a catchment that represents the snow depth for the whole catchment.The results from the developed model can be applied to facilitate the mapping and snow depth measurements in catchment areas, which can be used to streamline water regulation.

Master thesis is concerned with the subject of a snow cover dynamics (focused on snow melting) and of the detailed analysis of each physical-geographic factors effect on its character. Knowledges published in the domestic and foreign scientific literature are confronted with the data acquired within a number of expeditionary snow monitoring campaignes carried out during winter periods 2011/2012 a 2012/2013 in headwaters of rivers of Šumava (Šumava Mts., southwestern Czechia). Mobile field survey was done in a number of time horizons within the broadly conceived research in the upper Otava River basin concentrated on the assessment of the retention potential in headstream areas.