Abstract
Trying to obtain a more detailed understanding of the hydrological functioning of mountain catchments represents an important challenge in the effort of counteracting possible consequences of climate and land use change on water resources availability. Long-term (> 10 years) hydro-meteorological monitoring in small (typically < 10 km2) experimental catchments constitutes a valuable tool to achieve these goal. One of these sites is the Rio Vauz Catchment (1.9 km2), in the Italian Dolomites, that represents an excellent example of long-term snowmelt-dominated catchment in Dolomitic regions. The strong elevation gradient of the Rio Vauz Catchment and the different physiographic properties of its nested subcatchments make this a unique site for investigating fundamental runoff generation mechanisms in mountain headwaters. In this work, we provide a review of physical processes that have been inferred from 12 years of hydrological monitoring in this catchment. We present the available dataset and summarize the main hydrological mechanisms that explain the internal functioning of the Rio Vauz Catchment, primarily focusing on three characterizing hydrological behaviours, namely thresholds, hysteresis and connectivity. The main control on surface and subsurface runoff threshold response is constituted by a combination of soil moisture antecedent conditions, rainfall amount and topography. Changes in hysteresis patterns (clockwise and anti-clockwise loops) between streamflow and soil moisture, water table depth and electrical conductivity were governed by distinct runoff generation processes and rainfall event characteristics. Hillslope-riparian-stream subsurface connectivity was controlled by antecedent wetness conditions and rainfall amount. The composition in environmental tracers (stable isotopes of water and electrical conductivity) in different water sources and the application of tracer-based mixing models helped to distinguish the geographical sources to runoff and to quantify the role of rainfall and snowmelt in streamflow. Finally, we define a perceptual model of runoff generation processes for dry and wet conditions that can be considered representative for many mountain headwater catchments in the world.
Highlights
Small mountain catchments, especially in the headwater zones of large and populated basins, are important sources of fresh water necessary for human life
We introduce an overview on the tracer signature of different water compartments, we revise three main hydrological behaviours occurring in the catchment underlining the hydrological mechanisms at their base, and we conclude providing an overall description of runoff generation processes in Dolomitic mountain catchments
Within RVC, four subcatchments (Fig. 1) were instrumented for hydrometeorological monitoring: two rocky subcatchments representative of the upper part, Channel A (ChA) and Channel B (ChB), and two subcathments in the mid-lower part covered by grassland and sparse trees, Bridge Creek Catchment (BCC) and Larch Creek Catchment (LCC)
Summary
Especially in the headwater zones of large and populated basins, are important sources of fresh water necessary for human life. The Krycklan catchment (67.8 km2) with its subcatchments, in northern Sweden, which comprises a mosaic of wetland, lakes and forest, is likely the oldest long-term snowmelt-dominated experimental catchment It was established in 1920 with the aim to integrate research in water quality, hydrology and aquatic ecology in the boreal region. Very recent studies include the analysis of transit times (Amelia et al, 2016; Peralta-Tapia et al, 2016), streamflow variability (Karlsen et al, 2016; Teutschbein et al, 2016), hydrological thresholds and connectivity (Ali et al, 2015; Peralta-Tapia et al, 2015a, b), and water partitioning between vegetation and the other components of the water cycle (Tetzlaff et al, 2015) Another important site for hydrological processes understanding in snowmelt-dominated environments is the Hubbard Brook Experimental Forest, in the White Mountain National Forest (New Hampshire, USA). We introduce an overview on the tracer signature of different water compartments, we revise three main hydrological behaviours occurring in the catchment (thresholds, hysteresis, connectivity) underlining the hydrological mechanisms at their base, and we conclude providing an overall description of runoff generation processes in Dolomitic mountain catchments
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