Physically-based modelling of hydrological processes in a tropical headwater catchment in Benin (West Africa) – process representation and multi-criteria validation

Abstract. The aim of the study was to test the applicability of a physically-based model to simulate the hydrological processes in a headwater catchment in Benin. Field investigations in the catchment have shown that lateral processes as surface runoff and interflow are most important. Therefore the 1-D SVAT-model SIMULAT was modified to a hillslope version (SIMULAT-H). Due to a good database the model was evaluated in a multi-criteria validation using discharge, discharge components and spatially distributed soil moisture data. For the validation of discharge good results were achieved for dry and wet years. Main differences were observable in the beginning of the rainy season. The comparison of the discharge components determined by hydrochemical measurements with the simulation revealed that the model simulated the ratio of groundwater fluxes and fast runoff components correctly. For the validation of the discharge components of single events larger differences were observable, which was partly caused by uncertainties in the precipitation data. The representation of the soil moisture dynamics by the model was good for the top soil layer. For deeper soil horizons, which are characterized by higher gravel content, the differences between simulated and measured soil moisture were larger. Concerning the runoff generation processes a good agreement of simulation results and field investigations was achieved. On the upper and the middle slope interflow is the predominant process, while at the bottom of the hillslope groundwater recharge and – during the rainy season – saturated overland flow are important processes.

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Physically-based modelling of hydrological processes in a tropical headwater catchment (West Africa) – process representation and multi-criteria validation

Hydrology and Earth System Sciences ◽

10.5194/hess-10-829-2006 ◽

2006 ◽

Vol 10 (6) ◽

pp. 829-847 ◽

Cited By ~ 45

Author(s):

S. Giertz ◽

B. Diekkrüger ◽

G. Steup

Keyword(s):

Soil Moisture ◽

Rainy Season ◽

Overland Flow ◽

Soil Layer ◽

Hydrological Processes ◽

Runoff Generation ◽

Field Investigations ◽

Physically Based ◽

In The Beginning ◽

Headwater Catchment

Abstract. The aim of the study was to test the applicability of a physically-based model to simulate the hydrological processes in a headwater catchment in Benin. Field investigations in the catchment have shown that lateral processes such as surface runoff and interflow are most important. Therefore, the 1-D SVAT-model SIMULAT was modified to a semi-distributed hillslope version (SIMULAT-H). Based on a good database, the model was evaluated in a multi-criteria validation using discharge, discharge components and soil moisture data. For the validation of discharge, good results were achieved for dry and wet years. The main differences were observable in the beginning of the rainy season. A comparison of the discharge components determined by hydro-chemical measurements with the simulation revealed that the model simulated the ratio of groundwater fluxes and fast runoff components correctly. For the validation of the discharge components of single events, larger differences were observable, which was partly caused by uncertainties in the precipitation data. The representation of the soil moisture dynamics by the model was good for the top soil layer. For deeper soil horizons, which are characterized by higher gravel content, the differences between simulated and measured soil moisture were larger. A good agreement of simulation results and field investigations was achieved for the runoff generation processes. Interflow is the predominant process on the upper and the middle slopes, while at the bottom of the hillslope groundwater recharge and – during the rainy season – saturated overland flow are important processes.

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The influence of soil moisture on threshold runoff generation processes in an alpine headwater catchment

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-7-8091-2010 ◽

2010 ◽

Vol 7 (5) ◽

pp. 8091-8124 ◽

Cited By ~ 1

Author(s):

D. Penna ◽

H. J. Tromp-van Meerveld ◽

A. Gobbi ◽

M. Borga ◽

G. Dalla Fontana

Keyword(s):

Soil Moisture ◽

Overland Flow ◽

Riparian Zone ◽

Temporal Dynamics ◽

Runoff Generation ◽

Antecedent Conditions ◽

Antecedent Moisture ◽

Dry Conditions ◽

Strong Control ◽

Headwater Catchment

Abstract. This study investigates the role of soil moisture on the threshold runoff response in a small headwater catchment in the Italian Alps that is characterised by steep hillslopes and a distinct riparian zone. This study focuses on: (i) the threshold soil moisture-runoff relationship and the influence of catchment topography on this relation; (ii) the temporal dynamics of soil moisture, streamflow and groundwater that characterize the catchment's response to rainfall during dry and wet periods; and (iii) the combined effect of antecedent wetness conditions and rainfall amount on hillslope and riparian runoff. Our results highlight the strong control exerted by soil moisture on runoff in this catchment: a sharp threshold exists in the relationship between soil water content and runoff coefficient, streamflow, and hillslope-averaged depth to water table. Low runoff ratios were related to the response of the riparian zone, which was always close to saturation. High runoff ratios occurred during wet antecedent conditions, when the soil moisture threshold was exceeded. In these cases, subsurface flow was activated on hillslopes, which became major contributors to runoff. Antecedent wetness conditions also controlled the catchment's response time: during dry periods, streamflow reacted and peaked prior to hillslope soil moisture whereas during wet conditions the opposite occurred. This difference resulted in a hysteretic behaviour in the soil moisture-streamflow relationship. Finally, the influence of antecedent moisture conditions on runoff was also evident in the relation between cumulative rainfall and total stormflow. Small storms during dry conditions produced low runoff amounts, mainly from overland flow from the near saturated riparian zone. Conversely, for rainfall events during wet conditions, hillslopes contributed to streamflow and higher runoff values were observed.

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The influence of soil moisture on threshold runoff generation processes in an alpine headwater catchment

Hydrology and Earth System Sciences ◽

10.5194/hess-15-689-2011 ◽

2011 ◽

Vol 15 (3) ◽

pp. 689-702 ◽

Cited By ~ 213

Author(s):

D. Penna ◽

H. J. Tromp-van Meerveld ◽

A. Gobbi ◽

M. Borga ◽

G. Dalla Fontana

Keyword(s):

Soil Moisture ◽

Overland Flow ◽

Riparian Zone ◽

Temporal Dynamics ◽

Runoff Generation ◽

Antecedent Conditions ◽

Antecedent Moisture ◽

Dry Conditions ◽

Strong Control ◽

Headwater Catchment

Abstract. This study investigates the role of soil moisture on the threshold runoff response in a small headwater catchment in the Italian Alps that is characterised by steep hillslopes and a distinct riparian zone. This study focuses on: (i) the threshold soil moisture-runoff relationship and the influence of catchment topography on this relation; (ii) the temporal dynamics of soil moisture, streamflow and groundwater that characterize the catchment's response to rainfall during dry and wet periods; and (iii) the combined effect of antecedent wetness conditions and rainfall amount on hillslope and riparian runoff. Our results highlight the strong control exerted by soil moisture on runoff in this catchment: a sharp threshold exists in the relationship between soil water content and runoff coefficient, streamflow, and hillslope-averaged depth to water table. Low runoff ratios were likely related to the response of the riparian zone, which was almost always close to saturation. High runoff ratios occurred during wet antecedent conditions, when the soil moisture threshold was exceeded. In these cases, subsurface flow was activated on hillslopes, which became a major contributor to runoff. Antecedent wetness conditions also controlled the catchment's response time: during dry periods, streamflow reacted and peaked prior to hillslope soil moisture whereas during wet conditions the opposite occurred. This difference resulted in a hysteretic behaviour in the soil moisture-streamflow relationship. Finally, the influence of antecedent moisture conditions on runoff was also evident in the relation between cumulative rainfall and total stormflow. Small storms during dry conditions produced low stormflow amounts, likely mainly from overland flow from the near saturated riparian zone. Conversely, for rainfall events during wet conditions, higher stormflow values were observed and hillslopes must have contributed to streamflow.

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Impact of Climate and Land Use/Land Cover Change on the Water Resources of a Tropical Inland Valley Catchment in Uganda, East Africa

Climate ◽

10.3390/cli8070083 ◽

2020 ◽

Vol 8 (7) ◽

pp. 83

Author(s):

Geofrey Gabiri ◽

Bernd Diekkrüger ◽

Kristian Näschen ◽

Constanze Leemhuis ◽

Roderick van der Linden ◽

...

Keyword(s):

Climate Change ◽

Land Use ◽

Water Resources ◽

Land Cover ◽

Rainy Season ◽

Hydrological Processes ◽

Land Use Land Cover ◽

Lulc Change ◽

Inland Valley ◽

Headwater Catchment

The impact of climate and land use/land cover (LULC) change continues to threaten water resources availability for the agriculturally used inland valley wetlands and their catchments in East Africa. This study assessed climate and LULC change impacts on the hydrological processes of a tropical headwater inland valley catchment in Uganda. The hydrological model Soil and Water Assessment Tool (SWAT) was applied to analyze climate and LULC change impacts on the hydrological processes. An ensemble of six regional climate models (RCMs) from the Coordinated Regional Downscaling Experiment for two Representative Concentration Pathways (RCPs), RCP4.5 and RCP8.5, were used for climate change assessment for historical (1976–2005) and future climate (2021–2050). Four LULC scenarios defined as exploitation, total conservation, slope conservation, and protection of headwater catchment were considered. The results indicate an increase in precipitation by 7.4% and 21.8% of the annual averages in the future under RCP4.5 and RCP8.5, respectively. Future wet conditions are more pronounced in the short rainy season than in the long rainy season. Flooding intensity is likely to increase during the rainy season with low flows more pronounced in the dry season. Increases in future annual averages of water yield (29.0% and 42.7% under RCP4.5 and RCP8.5, respectively) and surface runoff (37.6% and 51.8% under RCP4.5 and RCP8.5, respectively) relative to the historical simulations are projected. LULC and climate change individually will cause changes in the inland valley hydrological processes, but more pronounced changes are expected if the drivers are combined, although LULC changes will have a dominant influence. Adoption of total conservation, slope conservation and protection of headwater catchment LULC scenarios will significantly reduce climate change impacts on water resources in the inland valley. Thus, if sustainable climate-smart management practices are adopted, the availability of water resources for human consumption and agricultural production will increase.

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Prediction of snowmelt derived streamflow in a wetland dominated prairie basin

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-7-1103-2010 ◽

2010 ◽

Vol 7 (1) ◽

pp. 1103-1141 ◽

Cited By ~ 2

Author(s):

X. Fang ◽

J. W. Pomeroy ◽

C. J. Westbrook ◽

X. Guo ◽

A. G. Minke ◽

...

Keyword(s):

Soil Moisture ◽

Hydrological Model ◽

Snow Accumulation ◽

Model Parameters ◽

Field Observations ◽

Runoff Generation ◽

Stream Channels ◽

Physically Based ◽

Set Up ◽

Spot 5

Abstract. The eastern Canadian Prairies are dominated by cropland, pasture, woodland and wetland areas. The region is characterized by many poor and internal drainage systems and large amounts of surface water storage. Consequently, basins here have proven challenging to hydrological model predictions which assume good drainage to stream channels. The Cold Regions Hydrological Modelling platform (CRHM) is an assembly system that can be used to set up physically based, flexible, object oriented models. CRHM was used to create a prairie hydrological model for the externally drained Smith Creek Research Basin (~400 km2), east-central Saskatchewan. Physically based modules were sequentially linked in CRHM to simulate snow processes, frozen soils, variable contributing area and wetland storage and runoff generation. Five "representative basins" (RBs) were used and each was divided into seven hydrological response units (HRUs): fallow, stubble, grassland, river channel, open water, woodland, and wetland as derived from a supervised classification of SPOT 5 imagery. Two types of modelling approaches calibrated and uncalibrated, were set up for 2007/08 and 2008/09 simulation periods. For the calibrated modelling, only the surface depression capacity of upland area was calibrated in the 2007/08 simulation period by comparing simulated and observed hydrographs; while other model parameters and all parameters in the uncalibrated modelling were estimated from field observations of soils and vegetation cover, SPOT 5 imagery, and analysis of drainage network and wetland GIS datasets as well as topographic map based and LiDAR DEMs. All the parameters except for the initial soil properties and antecedent wetland storage were kept the same in the 2008/09 simulation period. The model performance in predicting snowpack, soil moisture and streamflow was evaluated and comparisons were made between the calibrated and uncalibrated modelling for both simulation periods. Calibrated and uncalibrated predictions of snow accumulation were very similar and compared fairly well with the distributed field observations for the 2007/08 period with slightly poorer results for the 2008/09 period. Soil moisture content at a point during the early spring was adequately simulated and very comparable between calibrated and uncalibrated results for both simulation periods. The calibrated modelling had somewhat better performance in simulating spring streamflow in both simulation periods, whereas the uncalibrated modelling was still able to capture the streamflow hydrographs with good accuracy. This suggests that prediction of prairie basins without calibration is possible if sufficient data on meteorology, basin landcover and physiography are available.

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Dominant drivers of runoff in a slash-and-burn affected catchment in upland Eastern Madagascar

10.5194/egusphere-egu21-3957 ◽

2021 ◽

Author(s):

Bob W. Zwartendijk ◽

H.J. (Ilja) van Meerveld ◽

Ryan J. Teuling ◽

Chandra P. Ghimire ◽

L. Adrian Bruijnzeel

Keyword(s):

Soil Moisture ◽

Overland Flow ◽

Quantitative Information ◽

Forest Loss ◽

Runoff Generation ◽

Catchment Scale ◽

Valley Bottom ◽

Antecedent Soil Moisture ◽

Slash And Burn ◽

Slash And Burn Agriculture

In many tropical areas slash-and-burn agriculture is an important driver of forest loss. In areas where slash-and-burn agriculture has been practiced for decades, land cover is typically a mosaic of patches of remnant forest, fields under active cultivation, fallows in various stages of regrowth (ranging from young shrub to semi-mature), and degraded fire-climax grasslands. Although runoff generation mechanisms are expected to be different for these different patches, little quantitative information is available in this regard, particularly at the catchment scale and over longer time-scales (i.e., multiple slash-and-burn cycles).We re-instrumented a 31&#160;ha catchment in upland Eastern Madagascar, where slash-and-burn agriculture has been practiced for more than 70&#160;years in 2015; it had been monitored between 1963 and 1972 as well1. We measured streamflow at two locations and overland flow and soil moisture for four hillside plots (0.05 &#8211; 1.93&#160;ha): one plot under repeatedly coppiced and burned Eucalyptus and three plots under young shrub and tree fallows. One of the plots underwent rudimentary terracing in the past. We analysed the rainfall-runoff dynamics for 50&#160;rainfall events (median 12&#160;mm, maximum 71&#160;mm).For 60% of the events, the stormflow coefficient (minimum contributing area) was <3%, which is the proportion of valley-bottom wetlands and rice paddies in the catchment. Stable isotope sampling for five storm runoff events indicate a maximum total event-water contribution of 16%. However, instantaneous event-water contributions were as high as 66%. The hillside plot runoff response was dominated by saturation-excess overland flow and showed strong threshold behaviour in terms of the antecedent soil moisture storage in the upper 30 cm of the soil plus the event total rainfall amount (ASI + P). Average threshold values for overland flow occurrence ranged from 87 mm for the coppiced Eucalyptus to 137&#160;mm for the young fallow plots (regardless of terrace presence). Stormflow also increased after an ASI+P-threshold was exceeded (100&#160;mm based on the soil moisture sensors for the Eucalyptus plot and 150&#160;mm for the sensors at the tree fallow plots).These results indicate an increased hydrological connectivity between hillslopes and valley bottom under wetter conditions and that stormflow in the study catchment is strongly affected by variations in seasonal rainfall. The results will be used to validate a hydrological model to determine the net effect of concurrent changes in soil infiltrability and vegetation water use associated with forest loss and recovery on stormflow totals and the seasonal flow regime.1Bailly, C., de Coignac, G.B., Malvos, C., Ningre, J.M., and Sarrailh, J.M. (1974). &#201;tude de l'influence du couvert naturel et de ses modifications &#225; Madagascar. Exp&#233;rimentations en bassins versants &#233;l&#233;mentaires. Cahiers Scientifiques, 4. Centre Scientifique Forestier Tropical, Nogent-sur-Marne, France, 114 pp.

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Effects of antecedent soil moisture on runoff modeling in small semiarid watersheds of southeastern Arizona

Hydrology and Earth System Sciences ◽

10.5194/hess-15-3171-2011 ◽

2011 ◽

Vol 15 (10) ◽

pp. 3171-3179 ◽

Cited By ~ 30

Author(s):

Y. Zhang ◽

H. Wei ◽

M. A. Nearing

Keyword(s):

Soil Moisture ◽

Standard Deviation ◽

Soil Layer ◽

Arid Environment ◽

Storm Events ◽

Runoff Generation ◽

Antecedent Soil Moisture ◽

Small Watersheds ◽

Runoff Modeling ◽

Moisture Conditions

Abstract. This study presents unique data on the effects of antecedent soil moisture on runoff generation in a semi-arid environment, with implications for process-based modeling of runoff. The data were collected from four small watersheds measured continuously from 2002 through 2010 in an environment where evapo-transpiration approaches 100% of the infiltrated water on the hillslopes. Storm events were generally intense and of short duration, and antecedent volumetric moisture conditions were dry, with an average in the upper 5 cm soil layer over the nine year period of 8% and a standard deviation of 3%. Sensitivity analysis of the model showed an average of 0.05 mm change in runoff for each 1% change in soil moisture, indicating an approximate 0.15 mm average variation in runoff accounted for by the 3% standard deviation of measured antecedent soil moisture. This compared to a standard deviation of 4.7 mm in the runoff depths for the measured events. Thus the low variability of soil moisture in this environment accounts for a relative lack of importance of storm antecedent soil moisture for modeling the runoff. Runoff characteristics simulated with a nine year average of antecedent soil moisture were statistically identical to those simulated with measured antecedent soil moisture, indicating that long term average antecedent soil moisture could be used as a substitute for measured antecedent soil moisture for runoff modeling of these watersheds. We also found no significant correlations between measured runoff ratio and antecedent soil moisture in any of the four watersheds.

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Improving calibration and validation of cosmic-ray neutron sensors in the light of spatial sensitivity

Hydrology and Earth System Sciences ◽

10.5194/hess-21-5009-2017 ◽

2017 ◽

Vol 21 (10) ◽

pp. 5009-5030 ◽

Cited By ~ 35

Author(s):

Martin Schrön ◽

Markus Köhli ◽

Lena Scheiffele ◽

Joost Iwema ◽

Heye R. Bogena ◽

...

Keyword(s):

Soil Moisture ◽

Land Surface ◽

Cosmic Ray ◽

Water Dynamics ◽

Hydrological Processes ◽

Spatial Sensitivity ◽

Calibration And Validation ◽

Physically Based ◽

Point Data ◽

Neutron Sensors

Abstract. In the last few years the method of cosmic-ray neutron sensing (CRNS) has gained popularity among hydrologists, physicists, and land-surface modelers. The sensor provides continuous soil moisture data, averaged over several hectares and tens of decimeters in depth. However, the signal still may contain unidentified features of hydrological processes, and many calibration datasets are often required in order to find reliable relations between neutron intensity and water dynamics. Recent insights into environmental neutrons accurately described the spatial sensitivity of the sensor and thus allowed one to quantify the contribution of individual sample locations to the CRNS signal. Consequently, data points of calibration and validation datasets are suggested to be averaged using a more physically based weighting approach. In this work, a revised sensitivity function is used to calculate weighted averages of point data. The function is different from the simple exponential convention by the extraordinary sensitivity to the first few meters around the probe, and by dependencies on air pressure, air humidity, soil moisture, and vegetation. The approach is extensively tested at six distinct monitoring sites: two sites with multiple calibration datasets and four sites with continuous time series datasets. In all cases, the revised averaging method improved the performance of the CRNS products. The revised approach further helped to reveal hidden hydrological processes which otherwise remained unexplained in the data or were lost in the process of overcalibration. The presented weighting approach increases the overall accuracy of CRNS products and will have an impact on all their applications in agriculture, hydrology, and modeling.

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Effect of temporal rainfall distribution and soil type on soil moisture and runoff generation in semi-arid Zimbabwe

Hydrology Research ◽

10.2166/nh.2007.014 ◽

2007 ◽

Vol 38 (3) ◽

pp. 249-263 ◽

Cited By ~ 6

Author(s):

F.T. Mugabe ◽

M.G. Hodnett ◽

A. Senzanje

Keyword(s):

Soil Moisture ◽

Overland Flow ◽

Daily Rainfall ◽

Soil Surface ◽

Runoff Generation ◽

Stream Channels ◽

Wet Season ◽

Sodic Soils ◽

Rainfall Distribution ◽

Semi Arid

This paper examines the effect of temporal rainfall distribution on soil moisture and runoff generation in the 5.9 km2 Mutangi catchment in semi-arid Zimbabwe. Rainfall, soil moisture and runoff were measured during the 1999/00 and 2000/01 rainy seasons during which periods 755 mm and 615 mm of rainfall were received, respectively. The percentage of rainfall totals in these periods were 58% and 69%, respectively, in February. The total catchment runoff was 102 mm and 63 mm, of which 52% and 49% were recorded over 6 and 4 d in 2000 and 2001, respectively. Baseflow was negligible. Rainfall intensities were generally low. In the 1999/00 season there were 2 and 8 h with intensities >20 mm h−1 and 10 mm h−1, respectively. Some runoff appears to be generated by Hortonian overland flow (HOF), mainly in the early wet season before ploughing creates a rougher soil surface. The dominant process of runoff in this catchment was saturated overland flow (SOF), which occurs when the soils become saturated from below. The sodic soils along the stream channels appear to generate most of the runoff because of their small capacity to store water before saturation. The ridge soils are coarse sands, with a large capacity to store rainfall. The transitional (slope) soils have an intermediate capacity to store water. If there is a sequence of daily events that completely fills the storage available in both the sodic and transitional soils, and which begins to saturate the ridge soils, there could be very large amounts of runoff (>50% of the daily rainfall). The occurrence of such runoff events depends very heavily on the distribution of rainfall. Dry spells between rain events create storage, thereby reducing the risk of runoff from the next events.

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