@article{22560, abstract = {Grassland and pastures are important land uses in subalpine and alpine environments. They are typically subjected to management practices that can change the biophysical structure of the canopy through defoliation and can alter soil hydraulic properties. These modifications have the potential to impact hydrological and energy fluxes as well as the primary productivity of grasslands. We investigate how a series of management practices, such as grass cut, grazing, and the consequent soil compaction due to treading by animals are affecting water resources, flood generation, and grassland productivity in a subalpine region. Results are obtained using a mechanistic ecohydrological model, Tethys-Chloris. The model is first confirmed using energy, water, and carbon fluxes measured at three eddy covariance stations over grasslands in Switzerland and discharge measured in a small experimental catchment. A series of virtual experiments are then designed to elucidate the importance of various management scenarios at the plot and catchment scales. Results show that only severe management actions such as low grass cuts or heavy grazing are able to influence considerably the long-term hydrological behavior. Moderate management practices are typically unable to modify the system response in terms of energy and water fluxes. An important short-term effect is represented by animal-induced soil compaction that can reduce infiltration capacity leading to peak flow considerably higher than in undisturbed conditions. The productivity of vegetation in absence of nutrient limitation is considerably affected by the different management scenarios with tolerable disturbances that lead to higher aboveground net primary production.}, author = {Fatichi, Simone and Zeeman, Matthias J. and Fuhrer, Jürg and Burlando, Paolo}, issn = {1944-7973}, journal = {Water Resources Research}, number = {1}, pages = {148--164}, publisher = {American Geophysical Union}, title = {{Ecohydrological effects of management on subalpine grasslands: From local to catchment scale}}, doi = {10.1002/2013wr014535}, volume = {50}, year = {2014}, } @article{22508, abstract = {High-resolution space-time stochastic models for precipitation are crucial for hydrological applications related to flood risk and water resources management. In this study, we present a new stochastic space-time model, STREAP, which is capable of reproducing essential features of the statistical structure of precipitation in space and time for a wide range of scales, and at the same time can be used for continuous simulation. The model is based on a three-stage hierarchical structure that mimics the precipitation formation process. The stages describe the storm arrival process, the temporal evolution of areal mean precipitation intensity and wet area, and the evolution in time of the two-dimensional storm structure. Each stage of the model is based on appropriate stochastic modeling techniques spanning from point processes, multivariate stochastic simulation and random fields. Details of the calibration and simulation procedures in each stage are provided so that they can be easily reproduced. STREAP is applied to a case study in Switzerland using 7 years of high-resolution (2 × 2 km2; 5 min) data from weather radars. The model is also compared with a popular parsimonious space-time stochastic model based on point processes (space-time Neyman-Scott) which it outperforms mainly because of a better description of spatial precipitation. The model validation and comparison is based on an extensive evaluation of both areal and point scale statistics at hydrologically relevant temporal scales, focusing mainly on the reproduction of the probability distributions of rainfall intensities, correlation structure, and the reproduction of intermittency and wet spell duration statistics. The results shows that a more accurate description of the space-time structure of precipitation fields in stochastic models such as STREAP does indeed lead to a better performance for properties and at scales which are not used in model calibration.}, author = {Paschalis, Athanasios and Molnar, Peter and Fatichi, Simone and Burlando, Paolo}, issn = {1944-7973}, journal = {Water Resources Research}, number = {12}, pages = {8400--8417}, publisher = {American Geophysical Union}, title = {{A stochastic model for high-resolution space-time precipitation simulation}}, doi = {10.1002/2013wr014437}, volume = {49}, year = {2013}, } @article{12653, abstract = {Daily streamflow from stations close to five Swiss glaciers is analyzed for trends with the Mann-Kendall test. We consider a common period of record (1974–2004) and longer periods based on data availability. The trend statistical significance is tested on annual and seasonal bases. We also examine changes in precipitation, temperature, and snow cover characteristics. Highly glacierized basins show statistically significant positive trends in annual streamflow caused by increasing streamflow in spring and summer. Trends are more numerous and stronger at lower and mid than at the upper quantiles. The basin characterized by lower glacier coverage, conversely, does not exhibit consistently statistically significant trends. Changes in precipitation are not sufficient to explain the observed streamflow trends. Air temperature sees an increase in mean, minimum, and maximum values at all sites. Variations in the seasonal snow accumulation and ablation process are evident. Solid precipitation is decreasing at all sites and trends may be due to a shift from snowfall into rainfall. Mean snow depth is also decreasing, and its duration is getting shorter because of a decrease in solid precipitation and enhanced melting. Trend magnitude attenuates with longer time series. Contrasting trends are detected for different subperiods in the last 70 years: statistically significant negative trends are observed in the periods 1944–1974 and 1954–1984 for Aletschgletscher, in contrast with the results for the common period. These trends are explained by different rates of ice volume changes, and the sign of trends is clearly related to phases of positive or negative glacier mass balance.}, author = {Pellicciotti, Francesca and Bauder, A. and Parola, M.}, issn = {1944-7973}, journal = {Water Resources Research}, keywords = {Water Science and Technology}, number = {10}, publisher = {American Geophysical Union}, title = {{Effect of glaciers on streamflow trends in the Swiss Alps}}, doi = {10.1029/2009wr009039}, volume = {46}, year = {2010}, } @article{22446, abstract = {By partitioning mass and energy fluxes, soil moisture exerts a fundamental control on basin hydrological response. Using the design characteristics of the Biosphere 2 hillslope experiment, this study investigates aspects of soil moisture spatial and temporal variability in a zero‐order catchment of a semiarid climate. The hydrological response of the domain exhibits a particular structure, which depends on whether topography‐induced subsurface stormflow is triggered. The occurrence of the latter is conditioned by topography, soil depth, and pre‐storm spatial distribution of moisture. As a result, a non‐unique behavior of soil moisture spatial heterogeneity emerges, manifested through a hysteretic dependence of variability metrics on mean water content. Further, it is argued that vegetation dynamics impose a “homogenizing” effect on pre‐storm moisture states, decreasing the likelihood that a rainfall event will result in topographic redistribution of soil water. Consequently, post‐rainfall soil moisture dynamics associated with the effect of topography that could lead to the enhancement of spatial heterogeneity are suppressed; a potential “attractor” of catchment states emerges. The study thus proposes several hypotheses that will be testable within the framework of long‐term hillslope experiments.}, author = {Ivanov, Valeriy Y. and Fatichi, Simone and Jenerette, G. Darrel and Espeleta, Javier F. and Troch, Peter A. and Huxman, Travis E.}, issn = {1944-7973}, journal = {Water Resources Research}, number = {9}, publisher = {American Geophysical Union}, title = {{Hysteresis of soil moisture spatial heterogeneity and the “homogenizing” effect of vegetation}}, doi = {10.1029/2009wr008611}, volume = {46}, year = {2010}, }