scholarly journals Long‐term changes in runoff generation mechanisms for two proglacial areas in the Swiss Alps I: Overland Flow

2021 ◽  
Author(s):  
Fabian Maier ◽  
Ilja Meerveld
Keyword(s):  
Overland Flow ◽  
Swiss Alps ◽  
Runoff Generation ◽  
Long Term Changes ◽  
Generation Mechanisms

scholarly journals Rainfall-runoff processes in the Loess Plateau, China: Temporal dynamics of event rainfall-runoff characteristics and diagnostic analysis of runoff generation patterns

2020 ◽  
Author(s):  
Qiang Wu ◽  
Zhaoxi Zhang ◽  
Guodong Zhang ◽  
Shengqi Jian ◽  
Li Zhang ◽  
...  
Keyword(s):  
Loess Plateau ◽  
Time Scale ◽  
Overland Flow ◽  
Yellow River ◽  
Separation Procedure ◽  
Runoff Coefficient ◽  
Rainfall Runoff ◽  
Runoff Generation ◽  
The Loess Plateau

Abstract. The Loess Plateau is the most erosion-prone area in China, while under large-scale ecological restoration runoff and sediments continue to decrease. This study examined the runoff generation mechanism at the catchment scale to understand the change in runoff generation. Six baseflow used to separation method were tested and the nonparametric simple smoothing method was seperating base flow. With the event runoff separation procedure, 340 rainfall–runoff events are selected in five typical catchments affected by significant human intervention in the Loess Plateau. Runoff characteristics, such as the event runoff coefficient, time scale, rise time, and peak discharge are studied on monthly and long-term scales. In catchments of Jialuhe, Chabagou and Gushanchuan with poor vegetation runoff response is strongly decided by rainfall intensity and is produced by Horton overland flow (HOF). While the mountainous catchments of Jingle and Zulihe runoff response is controlled by rainfall volume. The relation between runoff event characteristics and rainfall is complicated in Loess Plateau, where rainfall and underlying surface is significantly changing. The monthly of event characteristics is mostly controlled by rainfall characteristics. Long-term runoff coefficient experiences decreasing trend, while time scale trend is increasing. Land use changes lead to increasing catchment wetness display mostly strong reason in event characteristic response. According to our proposed framework for classifying dominant runoff generation patterns considering of hydrograph response time, discharge source, and flow paths, HOF runoff is still the dominant mechanism, but gradually shifts to Dunne overland flow (DOF) and combination runoff. We speculate that the reduction in runoff in the Yellow River is likely to be the dominant runoff mechanism changing.

scholarly journals Response of the parameters of excess infiltration and excess storage model to land use cover change

2020 ◽  
Vol 68 (2) ◽  
pp. 99-110 ◽  
Author(s):  
Yuexiu Wen ◽  
Caihong Hu ◽  
Guodong Zhang ◽  
Shengqi Jian
Keyword(s):  
Land Use ◽  
Overland Flow ◽  
Yellow River ◽  
The Yellow River ◽  
Model Parameters ◽  
Runoff Generation ◽  
The Loess Plateau ◽  
Infiltration Capacity ◽  
Infiltration Excess ◽  
Generation Mechanisms

AbstractThe Loess Plateau is the main source of water in Yellow River, China. After 1980s, the Yellow river water presented a significant reduction, what caused the decrease of the Yellow river discharge had been debated in academic circles. We proceeded with runoff generation mechanisms to explain this phenomenon. We built saturation excess runoff and infiltration excess runoff generation mechanisms for rainfall–runoff simulation in Jingle sub-basin of Fen River basin on the Loess Plateau, to reveal the influence of land use change on flood processes and studied the changes of model parameters under different underlying conditions. The results showed that the runoff generation mechanism was mainly infiltration-excess overland flow, but the flood events of saturation-excess overland flow had an increasing trend because of land use cover change (the increase of forestland and grassland areas and the reduction of cultivated land). Some of the model parameters had physical significances，such as water storage capacity (WM), infiltration capacity (f), evapotranspiration (CKE), soil permeability coefficient (k) and index of storage capacity distribution curve (n) showed increasing trends, and index of infiltration capacity distribution curve (m) showed a decreasing trend. The above results proved the changes of runoff generation mechanism from the perspective of model parameters in Jingle sub-basin, which can provide a new perspective for understanding the discharge reduction in the Yellow River basin.

A hydrogeomorphic perspective on emergent topographic properties at landscape equilibrium

2021 ◽  
Author(s):  
David G. Litwin ◽  
Ciaran J. Harman ◽  
Gregory E. Tucker ◽  
Katherine R. Barnhart
Keyword(s):  
Overland Flow ◽  
Landscape Evolution ◽  
Subsurface Flow ◽  
Shallow Groundwater ◽  
Runoff Generation ◽  
Topographic Wetness Index ◽  
Topographic Analysis ◽  
Water Storage Capacity ◽  
Input Parameters

<p>Geomorphic properties of watersheds influence runoff generation, which drives landscape evolution over long timescales. Despite this strong process feedback, our understanding of how runoff generation affects long-term catchment evolution remains rudimentary. In most humid landscapes, storm runoff arises from shallow subsurface flow and from precipitation on saturated areas. Catchment geomorphology drives these runoff mechanisms, as landscape relief generates hydraulic gradients from hillslopes to streams, and regolith thickness and permeability affect flow partitioning and water storage capacity. However, there are few studies of how runoff coupled to dynamic shallow groundwater affects landscape form. In this study, we present a new groundwater-landscape evolution model and introduce a nondimensional framework to explore how subsurface-mediated runoff generation affects long-term catchment evolution. The model solves hydraulic groundwater equations to predict the water table location given prescribed recharge. Water in excess of the subsurface capacity for transport becomes overland flow, which may detach and transport sediment, affecting the landscape form that in turn affects runoff generation. We show that (1) two input parameters fully describe the possible steady state landscapes that coevolve under steady recharge, (2) subsurface flow capacity exerts a fundamental control on hillslope length and relief of these landscapes, and (3) three topographic metrics derived from the governing equations, steepness index, Laplacian curvature, and topographic wetness index, form a natural basis for evaluating the resulting coevolved landscapes. We derive a theoretical relationship using these metrics that allows us to recover the key model input parameters (including subsurface transmissivity) from topographic analysis of the landscape. These results open possibilities for topographic analysis of humid upland landscapes that could inform quantitative understanding of hydrological processes at the landscape scale.</p>

Young water fractions at diverse time scales are driven by varying runoff generation processes in a Mediterranean small research catchment

2020 ◽  
Author(s):  
Francesc Gallart ◽  
Pilar Llorens ◽  
Carles Cayuela ◽  
Matthias Sprenger ◽  
Jérôme Latron ◽  
...  
Keyword(s):  
Overland Flow ◽  
Stream Water ◽  
Special Role ◽  
Hydrograph Separation ◽  
Runoff Generation ◽  
Time Intervals ◽  
Water Fraction ◽  
Early Results ◽  
Generation Mechanisms ◽  
Large Discharge

<p>The time water resides within a catchment has important implications for the water availability and quality for both ecosystem and human use. Here, we look at the short-term water transport using the concept of young water fraction (<em>F<sub>yw</sub></em>), defined as the proportion of water that is younger than 2-3 months. The study was conducted for the 0.56 Km<sup>2</sup> sub-humid Can Vila catchment (Vallcebre Research Catchments). During a period of over 58 months, the isotope ratios (<sup>2</sup>H and <sup>18</sup>O) of rainwater was sampled at 5-mm rainfall intervals and stream water was sampled at variable time intervals (30 minutes to 1 week) depending on flow.</p><p>The early results of this research revealed intense dynamics of<em> F<sub>yw</sub></em> in relationship with discharge: <em>F<sub>yw</sub></em> had values between 0 for low flows and around 1 for the highest flows. Yet, the high variability of discharge and flashy response behaviour in this catchment along with the relatively large discharge sensitivity (<em>S<sub>d</sub></em>) of <em>F<sub>yw</sub></em> implied that even if the maximum sampled discharges were exceeded by only 0.01% of time, about 25% of the <em>F<sub>yw</sub></em> associated to the highest flows were estimated to be missed by the stream water sampling. This behaviour may be associated with a response dominated by saturation runoff generation mechanisms during wet episodes, which are known to drive the main hydrological response of this catchment.</p><p>Nevertheless, these results are obtained when all the samples are lumped for the whole 58 month period, but when different 12-month windows are investigated, the behaviour of <em>F<sub>yw</sub></em> becomes more intricate. Indeed, the wetter year was associated with the largest <em>F<sub>yw</sub></em> and <em>S<sub>d</sub></em> values, but drier years had irregularly varying values poorly correlated to precipitation or runoff statistics. Thus, other runoff generation mechanisms previously identified, including Hortonian-type overland flow in small degraded areas, that lead to runoff of new (and hence young) waters for low to moderate flows, will play a special role.</p><p>Current research is comparing <em>F<sub>yw</sub></em> analyses for groups of events of the same class, supported by hydrograph separation analyses and hydrometric indicators, for better understanding the dynamic and complex response of <em>F<sub>yw</sub></em> in this catchment. Our work further advances the understanding of limitations and opportunities of the <em>F<sub>y</sub><sub>w</sub></em> approach.</p>

Controls on streamwater age in a saturation overland flow-dominated catchment

2021 ◽  
Author(s):  
Dana Lapides ◽  
David Dralle ◽  
Daniella Rempe ◽  
William Dietrich ◽  
W. Jesse Hahm
Keyword(s):  
Overland Flow ◽  
Return Flow ◽  
Field Observations ◽  
Hydrograph Separation ◽  
Storm Events ◽  
Runoff Generation ◽  
Water Age ◽  
Flow Pathways ◽  
Generation Mechanisms ◽  
California Coast Ranges

<p>Water age and flow pathways should be related; however, it is still generally unclear how integrated catchment runoff generation mechanisms result in streamflow age distributions at the outlet. Here, we combine field observations of runoff generation at the Dry Creek catchment with StorAge Selection (SAS) age models to explore the relationship between streamwater age and runoff pathways. Dry Creek is an intensively monitored catchment in the northern California Coast Ranges with a Mediterranean climate and thin subsurface critical zone. Due to limited storage capacity, runoff response is rapid (~1-2 hours), and total annual streamflow consists predominantly of saturation overland flow, based on field mapping of saturated extents and runoff thresholds. Even though SAS modeling reveals that streamflow is younger at higher wetness states, flow is still typically older than one day and thus older than event water. Because streamflow is mostly overland flow, this means that a significant portion of overland flow must derive from groundwater returning to the surface, consistent with field observations of exfiltrating head gradients, return flow through macropores, and extensive saturation days after storm events. We conclude that even in a landscape with widespread overland flow, runoff pathways may be longer than anticipated, with implications for contaminant delivery and biogeochemical reactions. Our findings have implications for the assumptions built into classic hydrograph separation inferences, namely, that overland flow is not all new water.</p>

Isotopic hydrograph separation in a small agricultural catchment

2021 ◽  
Author(s):  
Borbála Széles ◽  
Juraj Parajka ◽  
Ladislav Holko ◽  
Stefan Wyhlidal ◽  
Katharina Schott ◽  
...  
Keyword(s):  
Overland Flow ◽  
Agricultural Land ◽  
Drainage System ◽  
Time Lapse ◽  
Tile Drainage ◽  
Hydrograph Separation ◽  
Runoff Generation ◽  
Agricultural Catchments ◽  
Two Component ◽  
Generation Mechanisms

<p>Exploring the isotopic composition of precipitation and streamflow in small catchments and the event and pre-event components of precipitation events using two-component isotopic hydrograph separation may better explain the overall catchment behaviour, more specifically the sources of water origin. This study’s main objective is to investigate the origin of water for different streamflow gauges in a small agricultural catchment, which represent different runoff generation mechanisms. The analysis will be performed in the Hydrological Open Air Laboratory (HOAL) in Austria, a 66 ha experimental catchment dominated by agricultural land use (Blöschl et al., 2016). One of the main specialities of this research catchment is that several tributaries of the catchment representing different runoff generation mechanisms are gauged, such as tile drainage flow or saturation excess runoff from erosion gullies. Two-component isotopic hydrograph separation (for both <sup>18</sup>O and <sup>2</sup>H) will be conducted for five streamflow gauges (catchment inlet and outlet, two erosion gullies and a tile drainage system) for multiple events in the period 2013-2018. The results will be linked and interpreted using additional observations such as time-lapse images of overland flow, electric conductivity measurements, groundwater level changes, evapotranspiration measurements, etc. The aim is to explain and discuss the processes of rainfall-runoff generation in small agricultural catchments.</p><p> </p><p>Reference:</p><p>Blöschl, G., et al. (2016). The Hydrological Open Air Laboratory (HOAL) in Petzenkirchen: A hypothesis‐driven observatory. Hydrol. Earth Syst. Sci., 20(1), 227–255. doi: 10.5194/hess‐20‐227‐2016.</p>

Surface runoff evolution on moraines in silicate and carbonate proglacial areas of the Swiss Alps

2020 ◽  
Author(s):  
Fabian Maier ◽  
Ilja van Meerveld
Keyword(s):  
Soil Water ◽  
Surface Runoff ◽  
Overland Flow ◽  
Landscape Evolution ◽  
Surface Characteristics ◽  
Surface Flow ◽  
Swiss Alps ◽  
Runoff Generation ◽  
Near Surface ◽  
Erosion Rates

<p>In many areas of the world, the surface of the earth is changing rapidly. Surface runoff is one of the processes that can dramatically modify the shape of our landscapes but is also affected by the land surface characteristics. However, our understanding of the evolution of overland flow characteristics and the feedback mechanisms between hydrological, pedological, biological and geormorphological processes that affect surface runoff is limited.</p><p>We used a space-for-time approach and studied 3 plots (4m x 6m each) on four different aged moraines (several decades to ~13.500 years) on the Sustenpass near the Steinglacier and in the karstic glacier foreland of the Griessfirn near Klausenpass (total of 24 plots) to determine how surface runoff generation changes during landscape evolution. We used artificial rainfall experiments with three different intensities to determine the surface flow ratio, peak flow rate, timing and duration of surface runoff. The addition of tracers (<sup>2</sup>H and salt) to the sprinkling water and sampling of soil water allowed identification of the mixing of the water within the slopes and the interaction of overland flow pathways with the subsurface. In addition, the runoff samples and sensor-based turbidity measurements provide an estimate of the erosion rates during extreme events. In order to link the differences in surface runoff generation with the pedological and biological characteristics of the slopes, soil and vegetation samples were taken on each plot to determine soil texture and root characteristics and the saturated hydraulic conductivity was measured in situ at three different depths.</p><p>The results show that the surface runoff amount and related erosion rates, response times and mixing of surface runoff and soil water change during landscape development and can largely be explained by related changes in soil surface and near surface characteristics. However, the rate of these changes during landscape evolution depends on the geology.</p>

scholarly journals Runoff generation in mountain catchments: long-term hydrological monitoring in the Rio Vauz Catchment, Italy

2018 ◽  
Vol 44 (2) ◽  
pp. 397 ◽  
Author(s):  
G. Zuecco ◽  
D. Penna ◽  
M. Borga
Keyword(s):  
Electrical Conductivity ◽  
Soil Moisture ◽  
Elevation Gradient ◽  
Rainfall Amount ◽  
Environmental Tracers ◽  
Runoff Generation ◽  
Threshold Response ◽  
Generation Mechanisms ◽  
Hydrological Monitoring

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.

Sign in / Sign up

Export Citation Format

Share Document