Linking slopes to the wetland: The relevance of interflow processes for water and nutrient input to an inland valley wetland in Uganda

2020 ◽  
Author(s):  
Claudia Schepp ◽  
Bernd Diekkrüger ◽  
Mathias Becker
Keyword(s):  
Land Use ◽  
Soil Water ◽  
Sandy Loam ◽  
Shallow Groundwater ◽  
Soil Surface ◽  
Shallow Aquifer ◽  
Nitrate Content ◽  
Small Scale ◽  
Infiltration Capacity ◽  
Inland Valley

<p>Due to their prolonged water availability wetlands are of increasing importance for small scale agriculture in East Africa. In the inundating landscape of central Uganda, inland valley wetlands are a common landscape unit with high potential for crop cultivation year-round. Yet little is known about the hydrological processes which bring out these favourable conditions. This study focusses on the relevance of interflow processes from the slopes into the wetland regarding water and nutrient delivery from different land use types. Hereby special attention is given to water pathways at the transition from upland geology to valley sediments and to nutrient relocation along the slopes.</p><p>Electrical Resistivity Tomography (ERT) was used as a non-invasive method to characterise interflow pathways in the highly variable saprolite geology and for subsurface delineation of the valley sediments. The measurements were complimented by a drilling campaign and infiltration experiments in different depths. Interflow collection pits were installed at the slope toe in order to quantify water and nutrient fluxes towards the wetland during two consecutive years. Additionally, soil moisture and nitrate content in the soil water were quantified at various positions along the slope.</p><p>ERT-imaging supports the hypothesis of a separation between a confined shallow aquifer and the soil water in the wetland sediments. Drilling results and hydrogeochemical analysis of the interflow and this shallow groundwater indicate a connection of the two components via macropores in the upper saprolite at the slope toe. At the same time interflow is transferred to the soil water of the wetland via a sandy loam layer which is found on top of the confining clay-loam layer of the wetland sediments. Both processes are active even during the dry season and therefore water from the interflow is relevant for water storage (shallow aquifer) and agricultural production (soil water) in the wetland.</p><p>Interflow volume and nitrate content both show a fast reaction to rainfall events, while the amount of water and nutrients delivered to the wetland is related to the land-use on the slope. Nitrate content in the soil water on the slopes suggests a relocation of nutrients in the upper soil horizons towards the slope toe. As infiltration capacity of the soil’s A-horizon is higher compared to the B-horizon a second  lateral flow component appears to be present close to the soil surface.</p><p>The results of this study emphasize the relevance of subsurface flow for wetland hydrology and give first explanations of wetland-upland connectivity in a complex saprolite geology.</p>

Evolution of groundwater chemistry on shallow aquifer of Yogyakarta City urban area

2015 ◽  
Vol 3 (2) ◽  
Author(s):  
Doni Prakasa Eka Putra
Keyword(s):  
Shallow Groundwater ◽  
Unconfined Aquifer ◽  
Groundwater Chemistry ◽  
Shallow Aquifer ◽  
Nitrate Content ◽  
New Business ◽  
Urban Settlements ◽  
A Minor ◽  
New Settlements ◽  
Yogyakarta City

Since 1980s, accelerated by urbanization, Yogyakarta City was shifting to many directions defined by main road networks and service centres. Urbanization has transformed rural dwellings to become urban settlements and generated urban agglomeration area. Until now, new business centres, education centres and tourism centres are growing hand in hand with new settlements (formal or informal) without proper provision of water supply and sanitation system. This condition increase the possibility of groundwater contamination from urban wastewater and a change of major chemistry of groundwater as shallow unconfined aquifer is lying under Yogyakarta City. To prove the evolution of groundwater chemistry, old data taken on 1980s were comparing with the recent groundwater chemistry data. The evaluation shows that nitrate content of groundwater in 1980s was a minor anion, but nowadays become a major anion, especially in the shallow groundwater in the centre of Yogyakarta City. This evidence shows that there is an evolution of groundwater chemistry in shallow groundwater below Yogyakarta City due to contamination from un-proper on-site sanitation system. Keywords: Urbanization, Yogyakarta city, rural dwellings, settlements, agglomeration, contamination, groundwater

Ammonia volatilization from surface-applied livestock slurry as affected by slurry composition and slurry infiltration depth

2006 ◽  
Vol 144 (3) ◽  
pp. 229-235 ◽  
Author(s):  
S. G. SOMMER ◽  
L. S. JENSEN ◽  
S. B. CLAUSEN ◽  
H. T. SØGAARD
Keyword(s):  
Soil Water ◽  
Dry Matter ◽  
Sandy Loam ◽  
Soil Water Potential ◽  
Soil Surface ◽  
Pig Slurry ◽  
Fertilizer Value ◽  
Loam Soil ◽  
Water Values ◽  
Slurry Composition

Volatilization of ammonia (NH3) from slurry applied in the field is considered a risk to the environment and reduces the fertilizer value of the slurry. To reduce volatilization a better understanding of the slurry–soil interaction is needed. Therefore, the present study focuses on measuring NH3 volatilization as affected by differences in infiltration. Livestock slurries with different dry matter (DM) composition and viscosity were included in the experiments by using untreated cattle and pig slurry, pig slurry anaerobically digested in a biogas plant and pig slurry anaerobically digested and physically separated. NH3 volatilization was measured using dynamic chambers and related to infiltration of the livestock slurries in the soil by measuring chloride (Cl−) and Total Ammoniacal Nitrogen (TAN=ammonium (NH4+)+NH3) concentrations in soil at different depths from 0·5 to 6·0 cm from the soil surface. The slurries were applied to sandy and sandy-loam soils packed in boxes within the chambers. There were no significant differences in relative volatilization of NH3 from untreated cattle and pig slurries, but anaerobic digestion of pig slurry increased volatilization due to increases in pH. However, physical separation of the digested slurry reduced the volatilization compared with untreated slurry, due to increased infiltration. In general, the volatilization decreased significantly with increased infiltration. The present study shows that NH3 volatilization from applied slurry can be related to infiltration and that infiltration is related to slurry composition (i.e. DM content and particle size distribution) and soil water content. The infiltration of liquid (measured by Cl− infiltration) was affected by soil water potential, therefore, Cl− infiltrated deeper into the sandy loam soil than the sandy soil at similar gravimetric soil water values. Dry matter (DM) and large particles (>1 mm) of the slurry reduced infiltration of liquid. A high proportion of small particles (<0·025 mm) facilitated infiltration of TAN.

Wheat root penetration and total available water on a range of soil types

1976 ◽  
Vol 16 (81) ◽  
pp. 570 ◽  
Author(s):  
D Tennant
Keyword(s):  
Shallow Water ◽  
Soil Water ◽  
Western Australia ◽  
Sandy Loam ◽  
Soil Surface ◽  
Wheat Root ◽  
Consistent Pattern ◽  
Clay Soils ◽  
Soil Types ◽  
Root Penetration

Depth of root penetration was examined over three years on a range of soil types in Western Australia. A consistent pattern was recognized. Roots penetrated rapidly to 5 to 10 cm from the soil surface within the first week from planting. Subsequent penetration was slow to 6 weeks, at which stage, depending on soil types, depth of root penetration was 15 to 30 cm. Rates of root penetration increased after 6 weeks from planting with greatest penetration occurring between 8 to 13 weeks. Respective maximum depths of root penetration in the deep sand, sandy loam, grey clay and sand over clay soils investigated were 169, 173, 31 and 73 cm. These depths were reached between 10 to 14 weeks after planting. Potential available soil water to maximum depths of root penetration were 2.6, 20.1, 5.6 and 8.1 cm for the deep sand, sandy loam, grey clay and sand over clay respectively. More than half of this available soil water was accessible for crop exploitation over the 9 to 14 week period after planting, except with shallow water and root penetration in the grey clay.

Land-use change and floods: what do we need most, research or management?

2002 ◽  
Vol 45 (8) ◽  
pp. 183-190 ◽  
Author(s):  
Arne Tollan
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Flood Risk ◽  
Human Impacts ◽  
Management Strategies ◽  
Flood Management ◽  
Flood Damage ◽  
Flood Frequency ◽  
Small Scale ◽  
Infiltration Capacity

Land-cover change (urbanisation, deforestation, and cultivation) results in increased flood frequency and severity. Mechanisms include reduced infiltration capacity, lower soil porosity, loss of vegetation, and forest clearing, meaning lower evapotranspiration. Major research challenges lie in quantification of effects in terms of flood characteristics under various conditions, ascertaining the combined effects of gradual changes over long time periods, and developing model tools suitable for land-use management. Large floods during the 1990s gave a new focus on these problems. Reference is made to the Norwegian HYDRA research programme on human impacts on floods and flood damage. The paper concludes that land-use change effects on floods are most pronounced at small scale and for frequent flood magnitudes. Model simulations of effects of land-use change can now be used to reduce flood risk. Modern flood management strategies have abandoned the position that dams and dikes are the only answers to mitigating flood disasters. Today, the strategic approach is more often: do not keep the water away from the people, keep people away from the water. Flood management strategies should include flood warnings, efficient communication, risk awareness, civil protection and flood preparedness routines, effective land-use policies, flood risk mapping, … as well as structural measures.

The role of soil water repellency in overland flow generation in pine and eucalypt forest stands in coastal Portugal

Soil Research ◽  
2005 ◽  
Vol 43 (3) ◽  
pp. 337 ◽  
Author(s):  
J. J. Keizer ◽  
C. O. A. Coelho ◽  
R. A. Shakesby ◽  
C. S. P. Domingues ◽  
M. C. Malvar ◽  
...  
Keyword(s):  
Soil Water ◽  
Overland Flow ◽  
Slope Angle ◽  
Soil Surface ◽  
Water Repellency ◽  
Rainfall Simulation ◽  
Soil Water Repellency ◽  
Infiltration Capacity ◽  
Eucalypt Forest ◽  
Flow Generation

Soil water repellency is now known to occur in diverse soils in various parts of the world. One of the possible adverse effects of soil water repellency is that it can reduce infiltration capacity and hence, on sloping terrain, enhance overland flow and soil erosion. The main aim of the present work is to assess the effects of soil water repellency on surface runoff production in the inner coastal dune areas of central Portugal. This was done for a pine and a eucalypt forest stand and, within each stand, for 2 slopes with contrasting aspect and somewhat different slope angles. Overland flow was measured for 4 pairs of unbounded plots of about 5 m2 at fortnightly intervals from February to October 2001. Over the same period, soil water repellency at and immediately below the soil surface was measured next to the plots at monthly intervals. The runoff–repellency relationship was also studied by carrying out rainfall simulation experiments on 0.24-m2 plots and associated repellency measurements. The effect of soil water repellency was most clearly demonstrated by statistically significant higher runoff coefficients under strong-to-extremely than under none-to-slightly hydrophobic conditions immediately below the soil surface. Such a difference in runoff over the measurement period was, however, restricted to 2 unbounded plots, both of which were located on the eucalypt slope with a southerly aspect and the greater slope angle. At the scale of these plots, the increase in runoff coefficient due to soil water repellency is moderate, when integrated over the entire period of strong–extremely repellent conditions, but can be quite substantial for individual 2-weekly periods. With respect to the observed differences in runoff between plots, be it plots on the same slope or not, it has proved difficult to distinguish the effect of soil water repellency from that of other factors likely to affect overland flow generation.

scholarly journals Water transmission properties of a sandy-loam soil estimated with Beerkan runs differing by the infiltration time criterion

2021 ◽  
Vol 69 (2) ◽  
pp. 151-160
Author(s):  
Vincenzo Bagarello ◽  
Gaetano Caltabellotta ◽  
Massimo Iovino
Keyword(s):  
Soil Water ◽  
Sandy Loam ◽  
Water Pressure ◽  
Soil Surface ◽  
Sandy Loam Soil ◽  
Water Volume ◽  
Transmission Properties ◽  
Time Criterion ◽  
Loam Soil ◽  
Water Transmission

Abstract The Beerkan method consists of a ponded infiltration experiment from a single ring inserted a small depth into the soil. Fixed, small volumes of water are repeatedly poured into the ring to maintain a quasi-zero head on the soil surface. According to the standard Beerkan infiltration run, a new water volume is poured on the infiltration surface when the previously applied volume has completely infiltrated and the soil surface is entirely exposed to air (ta criterion). However, water could also be applied when the soil exposition to air begins (to criterion) or half the soil surface is exposed to air (tm criterion). The effect of the infiltration time criterion on determination of the water transmission properties of a sandy-loam soil was tested. As compared with the standard ta criterion, the two alternative criteria (to , tm ) yielded higher and/or more variable estimates of soil water transmission properties. The saturated soil hydraulic conductivity, Ks , was the most sensitive property to the infiltration time criterion. However, statistically significant differences for Ks were not practically substantial since they did not exceed a factor of 1.7. Infiltration time effects likely occurred due to differences between ponding depth of water, soil water pressure head gradient, air entrapment and soil mechanical disturbance. The standard ta criterion was suggested for performing a Beerkan experiment in the field since it appears to yield the most reliable estimates of a mean value. However, the to criterion could be considered in dual permeability soils to maintain macropores active. Factors that could appear minor in the context of an experiment can have statistically relevant effects on water transmission properties.

scholarly journals Spring Characteristics and Hydrological Models of Catchments

1986 ◽  
Vol 17 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Jens-Olaf Englund
Keyword(s):  
Shallow Groundwater ◽  
Soil Surface ◽  
Potassium Nitrate ◽  
Natural Ecosystem ◽  
Infiltration Capacity ◽  
Quaternary Deposits ◽  
Main River ◽  
Calcium Magnesium ◽  
High Infiltration

The Åstdalen catchment (373 km2) represents largely a natural ecosystem, typical for the higher central and southern parts of the Scandinavian Peninsula. It is underlain by fractured sedimentary rocks with a thin cover of unconsolidated Quaternary deposits. The runoff process in Åstdalen is mainly determined by: Large accumulation of precipitation as snow, large areas covered by peatlands, and a high waterstorage capacity in the bedrocks. Groundwater discharge occurs in river beds, in springs and as flow towards the soil surface, especially toward peatland areas. The discharges of the main river Åsta and of investigated springs rise rapidly following snowmelt and rainstorms during the two water-years of study, 1 October 1980 to 30 September 1982. This shows that the catchment has a high infiltration capacity, and that water moves rapidly downslope in the saturated zone, following macropores in soils, peatlands and bedrock fractures. Groundwater, especially shallow groundwater, plays an important role of streamflow peak generation, even during snowmelt. About 60-70 % of the river discharges during the melting periods in 1981 and 1982 were baseflow. There is a net gain of protons, ammonium, potassium, nitrate and chloride to the catchment from the atmosphere during the year, and a net loss of calcium, magnesium sodium and sulfate. Constituents showing a net loss have an internal geologic and/or organic source in addition to the atmosphere. The concentration of most substances in river Åsta and in the investigated springs are lowered during peak flows. The concentration of protons is on the other hand typically increased during snowmelt. This indicates that fresh rain and/or snowmelt water dominates such flow periods and not older prestorm water. About 56 % of the protons needed to supply the weathering-derived ions to river Åsta come from precipitation.

Leaching of salts as affected by the method of water application and atmospheric evaporativity under shallow and saline water-table conditions

1987 ◽  
Vol 109 (3) ◽  
pp. 415-419 ◽  
Author(s):  
P. S. Minhas ◽  
B. K. Khosla
Keyword(s):  
Unsaturated Flow ◽  
Sandy Loam ◽  
Saline Water ◽  
Soil Depth ◽  
Shallow Groundwater ◽  
Soil Surface ◽  
Field Studies ◽  
Distinct Advantage ◽  
Upward Movement ◽  
Leaching Efficiency

SummaryField studies on leaching a highly saline sandy loam soil having a shallow groundwater table showed that application of 150 mm water in two equal parts at 10 days interval had no distinct advantage over a single application of the whole amount. On the contrary, the surface-accumulated salts were displaced to a lesser extent and the salt peak remained at a shallower depth under split application, particularly during periods of high atmospheric evaporativity when the leached salts tended to move upward between successive water applications. A soil mulch created by shallow tillage reduced evaporation losses and curtailed upward movement of salts, resulting in nearly 10% increase in leaching efficiency. Significantly a small quantity of water (0·41 cm leaching water per unit soil depth) sufficed for 70% chloride removal, indicating that under the prevailing conditions a larger fraction of the pores contributed to the leaching process. A compact layer, having a bulk density of 1·69 g/cm3, at the soil surface, also appeared to be related to the higher leaching efficiency by maintaining a preponderance of unsaturated flow.

scholarly journals Testing soil water repellency in a Sicilian area two years after a fire

2019 ◽  
Author(s):  
Vincenzo Bagarello ◽  
Giuseppe Basile ◽  
Gaetano Caltabellotta ◽  
Giuseppe Giordano ◽  
Massimo Iovino
Keyword(s):  
Soil Water ◽  
Water Drop ◽  
Soil Layer ◽  
Soil Surface ◽  
Water Repellency ◽  
Soil Conditions ◽  
Small Scale ◽  
Water Repellent ◽  
Soil Water Repellency ◽  
Mountain Area

The water drop penetration time (WDPT) technique was applied in 2018 to check persistence of soil water repellency (SWR) in a Sicilian mountain area affected by a wildfire on June 2016. A total of four sites, that were severely water repellent immediately after burning, were sampled. Depending on the site, wettable soil conditions, less SWR and maintenance of a noticeable SWR were detected two years later. At the site showing a near-constant SWR, WDPTs were particularly high in the top soil layer (0-0.03 m) and they appreciably decreased more in depth. Signs of decreasing SWR in drier soil conditions and in association with coarser soil particles were also detected at this site. High gradients of the WDPT can occur at very small vertical distances and a depth increment of approximately 0.01 m should be appropriate to capture small-scale vertical changes in SWR, especially close to the soil surface. Occurrence of SWR phenomena is easily perceivable and explainable if an inverse relationship between WDPTs and antecedent soil water content is obtained. A direct relationship between these two variables is more difficult to interpret because infiltration times that increase in wetter soil are expected according to the classical infiltration theory. A hypothesis that should be tested in the future is to verify if WDPTs that decrease in drier soil conditions signal less SWR as a consequence of a reduced biological activity of the soil. Finally, long-term monitoring projects on longevity of fire effects on SWR should be developed, even because an in depth knowledge of the involved processes is relevant for the civil protection system.

Infiltration of slurry liquid and volatilization of ammonia from surface applied pig slurry as affected by soil water content

1999 ◽  
Vol 132 (3) ◽  
pp. 297-303 ◽  
Author(s):  
S. G. SOMMER ◽  
O. H. JACOBSEN
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Surface ◽  
Fertilizer Efficiency ◽  
Nitrate Content ◽  
Pig Slurry ◽  
Soil Transport ◽  
Oligotrophic Ecosystems ◽  
Water Contents

Ammonia (NH3) volatilization may decrease the fertilizer efficiency of surface-applied slurry and may cause the unwanted deposition of nitrogen (N) in oligotrophic ecosystems. We studied the effect of soil water content on the infiltration of slurry liquid and how infiltration affected NH3 volatilization. NH3 volatilization was measured with dynamic chambers through which air was drawn continuously. Slurry spiked with bromide (Br−) to trace slurry infiltration was applied to a loamy sand in steel cylinders (diameter 6·7 cm and height 12 cm) adjusted to water contents of 0·01, 0·08, 0·12 and 0·19 g H2O per g soil (g g−1). At different time intervals after slurry application the soil columns were cut into slices and Br−, ammonium (NH4+) and nitrate (NO3−) concentrations were determined. At soil water contents >0·12 g g−1 nitrate content increased significantly from 24 to 72 h, and at 96 h NO3− content was equivalent to 75–130% of the NH4+ present at 0·5 h after slurry application. Nitrification may have contributed to a low NH3 volatilization from 24 to 96 h by reducing NH4+ concentration and contributing to acidity, and most of the NH3 volatilization occurred, therefore, during the first 24 h after application. Low soil water content enhanced the infiltration of slurry liquid and hence the mass transport of NH4+ into the soil. Transport of NH4+ by diffusion, on the other hand, was highest at the highest water content. Transport of NH4+ from the slurry at the soil surface down into the soil at 0·01 g g−1 reduced NH3 volatilization to c. 70% of the volatilization from slurry applied to soils at higher water contents. Diffusion of NH4+ into the soil did not significantly decrease NH3 volatilization.

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