Surface Runoff Rates Research Articles

Assessing the effects of land use change on soil physical properties and hydrological processes in the sub-humid tropical environment of West Africa

Land use is a key parameter in the hydrologic cycle. Tropical Africa is affected by intense land use change since decades, particularly deforestation and conversion to agricultural land. The aim of this study is to analyse the effects of land use change on the hydrologic processes and soil physical properties in a small catchment (Aguima catchment) in central Benin. Results from pedological, pedobiological and hydrological investigations within the Aguima catchment were taken into account. The effects of land use change on hydrologic processes were analysed by comparing two sub-catchments of the Aguima catchment with different land use (savannah/forest and agricultural land use). The study is part of the GLOWA IMPETUS project, which examines the effects of global change on the water cycle and water availability on a regional scale in Morocco and Benin. The investigations of this study revealed that due to reduced activity of the macrofauna the infiltration capacity is significantly lower in cultivated soils than in savannah and forest. This causes higher surface runoff and soil loss rates, which was also determined on erosion plots. The increased soil loss on fields has effects on soil physical properties like increase of gravel content and reduction of field capacity. The impact of reduced vegetation cover on the soil water dynamics was examined with soil moisture measurements on different land use. Due to higher evapotranspiration and water withdrawal the soil water content on forest and savannah plots was lower than on agricultural fields. The difference in the water yield of the forested and cultivated catchments was over 120 mm in the dry year 2001 and about 70 mm in the wetter year 2002.

Effects of soil degradation and management practices on the surface water dynamics in the Talgua River Watershed in Honduras

AbstractWhen tropical forests are felled, subsequent land uses affect surface runoff, soil erosion, and soil compaction. In some cases, they can markedly change the hydrology of a region with disastrous effects on human life. The objective of this paper is to investigate the effect of rainfall on stream hydrology due to conversion of primary forests to agriculture. Near surface water dynamics were compared for three land uses on the steep hillsides in the Talgua River Watershed in Honduras: degraded grass‐covered field; traditional coffee plantation; and primary forest. Infiltration and surface runoff rates were measured using several methods. A clear difference was observed in hydraulic conductivity between the degraded and non‐degraded lands. The degraded grass‐covered hillslopes developed a surface restrictive layer with a low saturated hydraulic conductivity of 8 to 11 mm/hr, resulting in more frequent overland flow than traditional coffee plantation and primary forest. Soils under the latter two land‐use types maintained high infiltration capacities and readily conducted water vertically at rates of 109 and 840 mm/hr, respectively. Dye tests confirmed that the coffee plantation and primary forest both maintained well‐connected macropores through which water flowed readily. In contrast, macropores in the degraded soil profile were filled by fine soil particles. Soils in the degraded grass‐covered field also showed more compaction than soils in the coffee plantation. Copyright © 2004 John Wiley & Sons, Ltd.

Surface and subsurface water balance estimation by the groundwater recharge model and a 3-D two-phase flow model/Estimation de bilan hydrologique de surface et de subsurface à l’aide de modèles de recharge de nappe et d’écoulement diphasique 3-D

Land development often results in adverse environmental impact for surface and subsurface water systems. For areas close to the coast, land changes may also result in seawater intrusion into coastal aquifers. Due to this, it is important to evaluate potential adverse effects in advance of any land development. For evaluation purposes a combined groundwater recharge model is proposed with a quasi three-dimensional unconfined groundwater flow equation. The catchment water balance for a planned new campus area of Kyushu University in southern Japan, was selected as a case study to test the model approach. Since most of the study area is covered with forest, the proposed groundwater recharge model considers rainfall interception by forest canopy. The results show that simulated groundwater and surface runoff agree well with observations. It is also shown that actual evapotranspiration, including rainfall interception by forest canopy, is well represented in the proposed simulation model. Several hydrological components such as direct surface runoff rate, groundwater spring flow rate to a ground depression, trans-basin groundwater flow etc., were also investigated.

Disposition of rainwater under creosotebush

AbstractIn desert shrubland ecosystems water and nutrients are concentrated beneath shrub canopies in ‘resource islands’. Rain falling on to these islands reaches the ground as either stemflow or throughfall and then either infiltrates into the soil or runs off as overland flow. This study investigates the partitioning of rainwater between stemflow and throughfall in the first instance and between infiltration and runoff in the second.Two series of 40 rainfall simulation experiments were performed on 16 creosotebush shrubs in the Jornada Basin, New Mexico. The first series of experiments was designed to measure the surface runoff and was performed with each shrub in its growth position. The second series was designed to measure stemflow reaching the shrub base and was conducted with the shrub suspended above the ground. The experimental data show that once equilibrium is achieved, 16% of the rainfall intercepted by the canopy or 6·7% of the rain falling inside the shrub area (i.e. the area inside the shrub's circumscribing ellipse) is funnelled to the shrub base as stemflow. This redistribution of the rainfall by stemflow is a function of the ratio of canopy area (i.e. the area covered by the shrub canopy) to collar area (i.e. a circular area centred on the shrub base), with stemflow rate being positively correlated and throughfall rate being negatively correlated with this ratio.The surface runoff rate expressed as a proportion of the rate at which rainwater arrives at a point (i.e. stemflow rate plus throughfall rate) is the runoff coefficient. A multiple regression reveals that 75% of the variance in the runoff coefficient can be explained by three independent variables: the rainfall rate, the ratio of the canopy area to the collar area, and the presence or absence of subcanopy vegetation. Although the last variable is a dummy variable, it accounts for 66·4% of the variance in the runoff coefficient. This suggests that the density and extent of the subcanopy vegetation is the single most important control of the partitioning of rainwater between runoff and infiltration beneath creosotebush. Although these findings pertain to creosotebush, similar findings might be expected for other desert shrubs that generate significant stemflow and have subcanopy vegetation. Copyright © 2003 John Wiley & Sons, Ltd.

Quantification and simulation of surface runoff from fescue grassland watersheds

The topographic features of the foothills fescue grasslands in southern Alberta predispose them to runoff and soil loss via erosion. A study was conducted at Stavely Research Station, Alberta to determine the runoff from small grassland watersheds under three grazing intensities, viz. ungrazed (or control), heavy (2.4 animal unit months per hectare (AUM ha −1)) and very heavy (4.8 AUM ha −1) grazing. Total annual precipitation in 1998, 1999 and 2000 was 648, 399 and 263 mm, respectively. Surface runoff hydrographs indicated large summer storm runoff rates from heavy grazed compared to other watersheds, but large snow melt-induced runoff from very heavy grazed compared to other watersheds. Surface runoff rates measured from May and August ranged between 0 and 2.3 mm per day in 1998, 0–0.2 mm per day in 1999, and 0–0.07 mm per day in 2000. In all the years, the average rainfall runoff was <10% of average daily precipitation on all three watersheds. In 2000, snow melt-induced runoff was measured in March. Total surface runoff for this month was 0.07, 8.5 and 3.7 mm for ungrazed, heavy and very heavy watersheds, respectively. These accounted for 78, 96 and 92% of total annual runoff from ungrazed, heavy and very heavy watersheds, respectively. Surface runoff for 1999 and 2000 was simulated using Soil Water Assessment Tool (SWAT), a continuous time distributed parameter model developed for ungaged basins. Model calibration was conducted using data of 1998 and parameters adjusted until the predicted and observed results were visibly close. Evaluation of the model was conducted using statistical criteria that included calculations of average error (AE), residual mean square (RMS), coefficient of residual mass (CRM) and modeling efficiency (EF), and comparing these statistics against optimal values. The evaluation indicated that the model under-predicted surface runoff from the watersheds in both the years.

Hillslope Runoff and Soil Erosion Following Reforestation in the Copper Basin, Tennessee, USA

The landscape of the 130 km2 Copper Basin, in the southeastern USA, became extremely degraded during more than a century of logging, mining, acidification, grazing, and fire. In the twentieth century, the Copper Basin became the focus of a series of reforestation programs and is now largely tree‐covered again. To investigate the effects of over 50 years of reforestation efforts, we developed a space‐for‐time substitution and conducted rainfall simulation experiments in ‘forest’ patches of various ages, at sites remaining unvegetated, and at forested reference sites outside the basin. At 59 sites, we monitored surface runoff and sediment detachment rates during 30‐minute rainfall simulation experiments; and at 54 of those sites, we determined soil organic matter content. Then, we measured litter and observed soils at 25 of the sites, and measured soil respiration at a site in each age zone. The results demonstrate that soil erosion by sediment detachment decreases within a decade following reforestation. Recently reforested sites have soils with significantly less organic matter and have higher runoff rates than forests more than 50 years old. The long‐term persistence of low infiltration rates suggests that, at sites where the A and B soil horizons and the biological health of the soil have been lost, restoration of the hydrologic function of a landscape by reforestation may require centuries.

Infiltration, runoff and sediment production in blanket peat catchments: implications of field rainfall simulation experiments

AbstractBlanket peat covers the headwaters of many major European rivers. Runoff production in upland blanket peat catchments is flashy with large flood peaks and short lag times; there is minimal baseflow. Little is known about the exact processes of infiltration and runoff generation within these upland headwaters. This paper presents results from a set of rainfall simulation experiments performed on the blanket peat moorland of the North Pennines, UK. Rainfall was simulated at low intensities (3–12 mm h−1), typical of natural rainfall, on bare and vegetated peat surfaces. Runoff response shows that infiltration rate increases with rainfall intensity; the use of low‐intensity rainfall therefore allows a more realistic evaluation of infiltration rates and flow processes than previous studies. Overland flow is shown to be common on both vegetated and bare peat surfaces although surface cover does exert some control. Most runoff is produced within the top few centimetres of the peat and runoff response decreases rapidly with depth. Little vertical percolation takes place to depths greater than 10 cm owing to the saturation of the peat mass. This study provides evidence that the quickflow response of upland blanket peat catchments is a result of saturation‐excess overland flow generation. Rainfall–runoff response from small plots varies with season. Following warm, dry weather, rainfall tends to infiltrate more readily into blanket peat, not just initially but to the extent that steady‐state surface runoff rates are reduced and more flow takes place within the peat, albeit at shallow depth. Sediment erosion from bare peat plots tends to be supply limited. Seasonal weather conditions may affect this in that after a warm, dry spell, surface desiccation allows sediment erosion to become transport limited. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Characteristics and Modeling of Runoff Hydrographs for Different Tillage Treatments

Surface runoff rate is a critical variable in determining the rate of soil erosion and sediment transport. Rainfall and runoff data at 1‐min intervals from an experiment site at Khon Kaen, Thailand, were used to test a three‐parameter runoff model originally developed for bare plots in relation to soil erosion studies. The site has a sandy soil with a slope of 3.6%. Plot length and width were 30 and 5 m, respectively. Four tillage treatments with three replicates each were considered: up‐ and down‐slope cultivation, two contour cultivation treatments with tillage depth of 25 and 50 cm, respectively, and no tillage. Runoff data for 200 individual runoff hydrographs showed that runoff amount and peak runoff rate for the no tillage treatment were significantly less than those for other treatments at the site. On average, runoff amount and peak runoff rate for the no tillage treatment were 37 and 44%, respectively, of those for the up‐ and down‐slope cultivation. Results for contour cultivation practices are between the two extremes, although the water retention was not greater with greater tillage depth as we originally thought would be the case at the site. For these 200 runoff events for the four treatments, the model for runoff hydrographs worked well, with an average coefficient of efficiency of 0.90 and an average standard error of 0.88 mm h−1 The model performance is particularly good for large storm events with high volumetric runoff coefficient. The three model parameters vary considerably from event to event and from treatment to treatment. The initial infiltration amount was found to be inversely related to prior 10‐d rainfall at the site; the spatially averaged maximum rate of infiltration can be related to the maximum retention or the Soil Conservation Service (SCS) Curve Number, and the hydrologic lag time is least variable among different storm events and tillage treatments, but tends to decrease with peak runoff rate.

DRAINMOD-N, A NITROGEN MODEL FOR ARTIFICIALLY DRAINED SOIL

DRAINMOD-N, a quasi two-dimensional model that simulates the movement and fate of nitrogen in shallow water table soils with artificial drainage, is described. Results of sensitivity analyses are presented and model predictions are compared with results from VS2DNT, a more complex, two-dimensional model. The nitrogen transport component is based on an explicit solution to the advective-dispersive-reactive (ADR) equation. Nitrate-nitrogen is the main N pool considered. Functional relationships are used to quantify rainfall deposition, fertilizer dissolution, net mineralization, denitrification, plant uptake, and surface runoff and subsurface drainage losses. A sensitivity analysis showed DRAINMOD-N predictions are most sensitive to the standard rate coefficients for denitrification and mineralization and nitrogen content in rainfall. Simulated daily water table depths were within 0.121 m, cumulative subsurface drainage rates were within 0.016 m, and cumulative surface runoff rates were within 0.003 m, of those predicted by VS2DNT for a 250-day period. DRAINMOD-N predictions for NO3-N losses in subsurface drainage water only differed from VS2DNT predictions by less than 2.6 kg ha–1. DRAINMOD-N predictions for denitrification were within 8%, for plant uptake were within 15%, and for net mineralization were within 26%, of those simulated by VS2DNT.

Erosion Response of a Disturbed Sagebrush Steppe Hillslope

AbstractLand management activities that disrupt surface vegetation cover pose a serious threat to the long‐term stability of buried‐waste sites located within the semiarid sagebrush (Artemisia tridentata Nutt.) steppe region of the northwestern USA. In this study, we evaluated the erosion response of a sagebrush hillslope subjected to three vegetation cover treatments: natural (undisturbed), bare (plant canopy and litter cover removed), and clipped (canopy removed). A rotating boom rainfall simulator was used to apply rain at 60 or 120 mm/h intensities to runoff plots (3.0 m by 10.7 m) with dry, wet, and very wet antecedent moisture conditions, and during two late and one early summer seasons. Supplemental overland flow was added at the upper end of each plot to simulate increased slope length during very wet runs. Maximum soil loss rates on the natural, clipped, and bare treatments were, respectively, 1, 5, and 216 mg/m2 per s during the 60 mm/h rainfall intensity, and 13, 79, and 1473 mg/m2 per s during the 120 mm/h rainfall intensity. Cumulative soil loss was typically 100 to 1000 times greater on the bare treatment than on the natural or clipped treatments. Increases in simulated slope length produced a near linear increase in soil loss from the bare treatment plots (about 0.02 g/m2 per s soil loss per m of slope length) until 30 m, after which the effect of slope length declined. Surface crust development and mound‐intermound microtopography played important roles in governing soil detachment and transport on the hillslope. Despite high rainfall intensity and surface runoff rates, rill erosion was negligible on both the undisturbed and disturbed portions of the hillslope.

Field Evaluation of Shallow Subsurface Drains to Vent Soil Air, Improve Infiltration, and Reduce Runoff

ABSTRACT The effect of soil air entrapment on surface runoff rate and quantity was evaluated in the field using shallow subsurface drainage and tillage treatments to modify the amount of air trapped in a fragipan soil. The volume of pore space filled with air was increased by tillage and subsurface drainage. The latter also vented entrapped soil air during infiltration events. When the entrapped soil air was vented through the drain, the average steady-state subsurface drainage rate increased 20.9 and 48.9% for grass vegetated and tilled fallow conditions, respectively. Corresponding decreases in steady state surface runoff rates were 10.4 and 14.9%, respectively. Venting air pressure, as low as 40 Pa (gauge) resulted in an increase in drain flow rate and a decrease in runoff rate. Generally, lower soil air pressures during infiltration occurred in the vegetated soil because cracking along soil aggregate faces induced by transpirational drying provided for some surface venting. As a result, soil air pressure declined more during an extended infiltration event in the grass plot than in the fallow plot. The immediate result of tillage followed by precipitation was greater infiltration and soil water retention, however as reconsolidation occurred, soil air entrapment increased and a greater portion of the applied water became surface runoff. After reconsolidation caused by 627.6 mm of precipitation, air entrapment pressure of 1.36 kPa resulted in a 36.0% decrease in tile flow rate and 20.5% increase in surface runoff rate. Likewise, with reconsolidation air entrapment pressure of 2.41 kPa resulted in an 8.8% decrease in tile flow and 32.9% increase in surface runoff volumes.

Chemical Transport from Coastal Plain Soils Under Simulated Rainfall: L Surface Runoff, Percolation, Nitrate, and Phosphate Movement

ABSTRACT Astudy was conducted to determine amounts and rates of surface runoff, percolation, nitrate and phosphate movement from the upper root zone of three upland Coastal Plain soils. Surface soil samples of Greenville sandy clay loam. Red Bay loamy sand, and Bonifay sand were packed into rectangular stainless steel boxes equipped with surface runoff and percolate collection devices. The soils ranged in clay content from 29.3% to 3.6%, and represented a range of soil textures commonly found in the Coastal Plain. Simulated rainfall was applied to each soil at high (125 mm/hr), medium (75 mm/hr), or low (43 mm/hr) intensities. Surface runoff rates varied from none to about 100 mm/hr depending on soil texture, crusting and sealing, and rainfall intensity. Percolation was found to be the major water-loss pathway on the sandier soils at the lower rainfall intensities. Surface runoff was the major water-loss pathway at the high rainfall intensity on the Bonifay sand (69.8%), and for all three rainfall intensities on the Greenville sandy clay loam. The study showed that percolation is the major pathway for NO3-N movement from the upper root zone of the sandier Coastal Plain soils. Some PO4 moved with percolation on the two sandier soils, but not on the clayey soil. Nitrate and PO4 movement from the clayey soil was primarily in surface runoff. Comparison of NO3-N and PO4 movement predictions made by the GLEAMS model with actual observations showed that the model worked best on the sandier soils. The study indicates that care should be taken to avoid applying NO3-N and PO4 when probability for immediate intense rainfall is great.

Comparison of Four Infiltration Models in Characterizing Infiltration through Surface Mine Profiles

ABSTRACT Alaboratory infiltrometer system was used to evaluate the infiltration process through reconstructed surface mine profiles. Six different profiles were subjected to constant simulated rainfall intensities for selected test conditions. Surface runoff rates were monitored and transient soil moisture contents in the profiles were measured with a gamma density gauge. Unsaturated hydraulic conductivity relationships were determined using Campbelfs method and the zero-flux procedure. The infiltration process was modeled by the SCS curve number method, a form of Holtan's equation, the Green-Ampt model and Richards' equation. SCS curve numbers were determined by fitting the method to the observed results. Richards' equation gave very good estimates of the infiltration process through the spoil profiles, but was only slightly better than the Green-Ampt model. None of the models worked well for the profiles where macropore flow occurred through a two layer, topsoil-over-spoil system.

Hydrology and Chemical Quality of Flow from Small Pastured Watersheds: I. Hydrology

AbstractSurface runoff, soil loss, and subsurface flow were measured from four rotationally grazed summer pastures. One of these pastures was also used as a winter‐feeding area. Surface runoff volumes and peak rates from the three pastures used only for summer grazing were generally less as compared with values for earlier years when the fields were in meadow and fight pasturing; however, runoff from the winterfeeding area was markedly increased. Both before and after the initiation of grazing, the areas used only for summer grazing had but a trace of soil loss. More soil was lost from the winter‐feeding area, particularly during the dormant season. Water‐balance studies indicated that during the growing season surface runoff and subsurface outflow were higher and evapotranspiration (ET) was less from the winter‐feeding area than from areas summer‐grazed only. During the dormant season, surface runoff was higher and subsurface outflow was lower from the winter‐feeding area than from the summer‐grazed areas, whereas ET was similar.

PARTIAL AREA RESPONSE ON SMALL SEMIARID WATERSHEDS1

ABSTRACT: Significant errors in estimating surface runoff and erosion rates are possible if a watershed is assumed to contribute runoff uniformly over the entire area, when actually only a portion of the entire area may be contributing. Generation of overland flow on portions of small semiarid watersheds was analyzed by three methods: an average loss rate procedure, a lumped‐linear model, and a distributed‐nonlinear model. These methods suggested that, on the average, 45, 60, and 50% of the drainage area was contributing runoff at the watershed outlet. Infiltrometer data support the partial area concept and indicate that the low infiltration zones are the runoff source areas as simulated with the distributed‐nonlinear model.

Leachability of a Wetting Agent Treatment for Water-Resistant Soils

Burned chaparral watersheds in southern California have been found to possess a “nonwettable” soil property. This resistance to wetting is believed to be instrumental in producing high surface runoff and erosion rates during storm periods. A laboratory leaching study was conducted to estimate the teachability of a remedial wetting agent treatment in this problem soil. Results from the study showed that the wetting agent treatment persisted after 40 cm of water have passed through the soil samples.