Bedrock geology controls on catchment storage,mixing, and release: A comparative analysis of 16 nested catchments          下载免费PDF全文

Laurent Pfister  Núria Martínez‐Carreras  Christophe Hissler  Julian Klaus  Gwenael E. Carrer  Mike K. Stewart  Jeffrey J. McDonnell 《水文研究》2017,31(10):1828-1845

The bedrock controls on catchment mixing, storage, and release have been actively studied in recent years. However, it has been difficult to find neighbouring catchments with sufficiently different and clean expressions of geology to do comparative analysis. Here, we present new data for 16 nested catchments (0.45 to 410 km²) in the Alzette River basin (Luxembourg) that span a range of clean and mixed expressions of schists, phyllites, sandstones, and quartzites to quantify the relationships between bedrock permeability and metrics of water storage and release. We examined 9 years' worth of precipitation and discharge data, and 6 years of fortnightly stable isotope data in streamflow, to explore how bedrock permeability controls (a) streamflow regime metrics, (b) catchment storage, and (c) isotope response and catchment mean transit time (MTT). We used annual and winter precipitation–run‐off ratios, as well as average summer and winter precipitation–run‐off ratios to characterise the streamflow regime in our 16 study catchments. Catchment storage was then used as a metric for catchment comparison. Water mixing potential of 11 catchments was quantified via the standard deviation in streamflow δD (σδD) and the amplitude ratio (A_S/A_P) of annual cycles of δ¹⁸O in streamflow and precipitation. Catchment MTT values were estimated via both stable isotope signature damping and hydraulic turnover calculations. In our 16 nested catchments, the variance in ratios of summer versus winter average run‐off was best explained by bedrock permeability. Whereas active storage (defined here as a measure of the observed maximum interannual variability in catchment storage) ranged from 107 to 373 mm, total catchment storage (defined as the maximum catchment storage connected to the stream network) extended up to ~1700 mm (±200 mm). Catchment bedrock permeability was strongly correlated with mixing proxies of σδD in streamflow and δ¹⁸O A_S/A_P ratios. Catchment MTT values ranged from 0.5 to 2 years, based on stable isotope signature damping, and from 0.5 to 10 years, based on hydraulic turnover.  相似文献   

Attribution of changes in the water balance of a tropical catchment to land use change using the SWAT model   总被引：1，自引：0，他引：1       下载免费PDF全文

Hero Marhaento  Martijn J. Booij  T.H.M. Rientjes  Arjen Y. Hoekstra 《水文研究》2017,31(11):2029-2040

Changes in the water balance of the Samin catchment (277.9 km²) on Java, Indonesia, can be attributed to land use change using the Soil Water Assessment Tool model. A baseline‐altered method was used in which the simulation period 1990–2013 was divided into 4 equal periods to represent baseline conditions (1990–1995) and altered land use conditions (1996–2001, 2002–2007, and 2008–2013). Land use maps for 1994, 2000, 2006, and 2013 were acquired from satellite images. A Soil Water Assessment Tool model was calibrated for the baseline period and applied to the altered periods with and without land use change. Incorporating land use change resulted in a Nash–Sutcliffe efficiency of 0.7 compared to 0.6 when land use change is ignored. In addition, the model performance for simulations without land use change gradually decreased with time. Land use change appeared to be the important driver for changes in the water balance. The main land use changes during 1994–2013 are a decrease in forest area from 48.7% to 16.9%, an increase in agriculture area from 39.2% to 45.4%, and an increase in settlement area from 9.8% to 34.3%. For the catchment, this resulted in an increase of the runoff coefficient from 35.7% to 44.6% and a decrease in the ratio of evapotranspiration to rainfall from 60% to 54.8%. More pronounced changes can be observed for the ratio of surface runoff to stream flow (increase from 26.6% to 37.5%) and the ratio of base flow to stream flow (decrease from 40% to 31.1%), whereas changes in the ratio of lateral flow to stream flow were minor (decrease from 33.4% to 31.4%). At sub‐catchment level, the effect of land use changes on the water balance varied in different sub‐catchments depending on the scale of changes in forest and settlement area.  相似文献   

Biomorphological scaling laws from convectively accelerated streams     

Giulio Calvani  Paolo Perona  Coralie Schick  Luca Solari 《地球表面变化过程与地形》2020,45(3):723-735

Worldwide convectively accelerated streams flowing in downstream-narrowing river sections show that riverbed vegetation growing on alluvial sediment bars gradually disappears, forming a front beyond which vegetation is absent. We revise a recently proposed analytical model able to predict the expected longitudinal position of the vegetation front. The model was developed considering the steady state approximation of 1-D ecomorphodynamics equations. While the model was tested against flume experiments, its extension and application to the field is not trivial as it requires the definition of proper scaling laws governing the observed phenomenon. In this work, we present a procedure to calculate vegetation parameters and flow magnitude governing the equilibrium at the reach scale between hydromorphological and biological components in rivers with converging boundaries. We collected from worldwide rivers data of section topography, hydrogeomorphological and riparian vegetation characteristics to perform a statistical analysis aimed to validate the proposed procedure. Results are presented in the form of scaling laws correlating biological parameters of growth and decay from different vegetation species to flood return period and duration, respectively. Such relationships demonstrate the existence of underlying selective processes determining the riparian vegetation both in terms of species and cover. We interpret the selection of vegetation species from ecomorphodynamic processes occurring in convectively accelerated streams as the orchestrated dynamic action of flow, sediment and vegetation characteristics. © 2019 John Wiley & Sons, Ltd.  相似文献   

Geomorphological evolution and sediment stratigraphy of numerically simulated alluvial fans     

W.D. Dimuth P. Welivitiya  Garry R. Willgoose  Greg R. Hancock 《地球表面变化过程与地形》2020,45(9):2148-2166

When a sediment laden river reaches a flat basin area the coarse fraction of their sediment load is deposited in a cone shaped structure called an alluvial fan. In this article we used the State Space Soil Production and Assessment Model (SSSPAM) coupled landform–soilscape evolution model to simulate the development of alluvial fans in two- and three-dimensional landforms. In SSSPAM the physical processes of erosion and armouring, soil weathering and sediment deposition were modelled using state-space matrices, in both two and three dimensions. The results of the two-dimensional fan showed that the fan grew vertically and laterally keeping a concave up long profile. It also showed a downstream fining of the sediments along the fan profile. Both of these observations are in agreement with available literature concerning natural and experimental fan formations. Simulations with the three-dimensional landform produced a fan with a semicircular shape with concave up long profiles and concave down cross profiles which is typical for fans found in nature and ones developed in laboratory conditions. During the simulation the main channel which brings sediment to the fan structure changed its position constantly leading to the semicircular shape of the fan. This behaviour is similar to the autogenic process of ‘fanhead trenching’ which is the major mechanism of sediment redistribution while the fan is developing. The three-dimensional fan simulation also exhibited the downstream fining of sediments from the fan apex to the peripheries. Further, the simulated fan also developed complex internal sediment stratification which is modelled by SSSPAM. Currently such complex sediment stratification is thought to be a result of allogenic processes. However, this simulation shows that, such complex internal sediment structures can develop through autogenic processes as well. © 2020 John Wiley & Sons, Ltd.  相似文献   

Interaction of wind and cold-season hydrologic processes on erosion from complex topography following wildfire in sagebrush steppe     

Samantha P. Vega  C. Jason Williams  Erin S. Brooks  Frederick B. Pierson  Eva K. Strand  Peter R. Robichaud  Robert E. Brown  Mark S. Seyfried  Kathleen A. Lohse  Kayla Glossner  Jennifer L. Pierce  Clay Roehner 《地球表面变化过程与地形》2020,45(4):841-861

Wildfire is a natural component of sagebrush (Artemisia spp.) steppe rangelands that induces temporal shifts in plant community physiognomy, ground surface conditions, and erosion rates. Fire alteration of the vegetation structure and ground cover in these ecosystems commonly amplifies soil losses by wind- and water-driven erosion. Much of the fire-related erosion research for sagebrush steppe has focused on either erosion by wind over gentle terrain or water-driven erosion under high-intensity rainfall on complex topography. However, many sagebrush rangelands are geographically positioned in snow-dominated uplands with complex terrain in which runoff and sediment delivery occur primarily in winter months associated with cold-season hydrology. Current understanding is limited regarding fire effects on the interaction of wind- and cold-season hydrologic-driven erosion processes for these ecosystems. In this study, we evaluated fire impacts on vegetation, ground cover, soils, and erosion across spatial scales at a snow-dominated mountainous sagebrush site over a 2-year period post-fire. Vegetation, ground cover, and soil conditions were assessed at various plot scales (8 m² to 3.42 ha) through standard field measures. Erosion was quantified through a network of silt fences (n = 24) spanning hillslope and side channel or swale areas, ranging from 0.003 to 3.42 ha in size. Sediment delivery at the watershed scale (129 ha) was assessed by suspended sediment samples of streamflow through a drop-box v-notch weir. Wildfire consumed nearly all above-ground live vegetation at the site and resulted in more than 60% bare ground (bare soil, ash, and rock) in the immediate post-fire period. Widespread wind-driven sediment loading of swales was observed over the first month post-fire and extensive snow drifts were formed in these swales each winter season during the study. In the first year, sediment yields from north- and south-facing aspects averaged 0.99–8.62 t ha⁻¹ at the short-hillslope scale (~0.004 ha), 0.02–1.65 t ha⁻¹ at the long-hillslope scale (0.02–0.46 ha), and 0.24–0.71 t ha⁻¹ at the swale scale (0.65–3.42 ha), and watershed scale sediment yield was 2.47 t ha⁻¹. By the second year post fire, foliar cover exceeded 120% across the site, but bare ground remained more than 60%. Sediment yield in the second year was greatly reduced across short- to long-hillslope scales (0.02–0.04 t ha⁻¹), but was similar to first-year measures for swale plots (0.24–0.61 t ha⁻¹) and at the watershed scale (3.05 t ha⁻¹). Nearly all the sediment collected across all spatial scales was delivered during runoff events associated with cold-season hydrologic processes, including rain-on-snow, rain-on-frozen soils, and snowmelt runoff. Approximately 85–99% of annual sediment collected across all silt fence plots each year was from swales. The high levels of sediment delivered across hillslope to watershed scales in this study are attributed to observed preferential loading of fine sediments into swale channels by aeolian processes in the immediate post-fire period and subsequent flushing of these sediments by runoff from cold-season hydrologic processes. Our results suggest that the interaction of aeolian and cold-season hydrologic-driven erosion processes is an important component for consideration in post-fire erosion assessment and prediction and can have profound implications for soil loss from these ecosystems. © 2019 John Wiley & Sons, Ltd.  相似文献