Upper Part Of Catchment Research Articles

Urbanization—Its Hidden Impact on Water Losses: Prądnik River Basin, Lesser Poland

Urban development causes multiple water losses. Some of them may be ignored but some could have a huge influence on the whole catchment, including soil drought. As urban sprawl rises, space for unaffected infiltration and retention is increasingly limited. The objective of this study was to backcast and to estimate water-retention loss due to urbanization during the period of 1990–2018. We used landcover data, meteorological and hydrological data and data on soil water-holding capacity. Water-retention loss was expressed as soil water retention capacity loss, net precipitation loss and total sum of precipitation loss. Historical change in urban extension has led to large impacts on the hydrological cycle of the study area. Progressive urban development caused water-retention losses which range from 3.380 to 14.182 millions of cubic meters—depending on the methodology used. Hydrological analysis showed the lack of a significant trend (decrease trend) of low flow which is caused by the high percentage of natural land use in the upper part of catchment. Our results show that backcasting of water retention change using CLC data (a) brings new and plausible data on retention loss, (b) is possible to replicate and (c) data used are common and easy-to-get.

Decadal Trends of Soil Loss and Runoff in the Koga Catchment, Northwestern Ethiopia

AbstractThis study used the physically based distributed Annualized Agricultural Non‐Point Source model to simulate decadal trends in soil loss and runoff with changes in land use/cover in the 98·4 km2 upper part of the Koga catchment. The study indicated that soil loss in the study area has increased from 17 Mg ha−1 y−1 in 1957 to 25 Mg ha−1 y−1 in 2010 because of a decrease in the amount of woody vegetation cover. We found that over the past 50 years, high risk erosion areas with soil loss greater than 35 Mg ha−1 y−1 covered, on average, 41% of the study area, while these same areas contributed, on average, 78% of the soil loss from the study area. Twenty one percent of the study area has been in the high risk erosion category throughout all the years since 1957. The total amount of soil loss from the study area varied with changes in the amount of woody vegetation cover. Other factors such as landforms and soil type also affected the amount of soil erosion. Whereas most of the high erosion areas were found in the upper part of the catchment, most of the high runoff areas were found in the lower part of the catchment, indicating that the amount of soil erosion is not directly related to runoff volume in the study area. Crop fields contributed to most of the soil loss in the study area. Copyright © 2015 John Wiley & Sons, Ltd.

A landscape-scale approach to examining the fate of atmospherically derived industrial metals in the surficial environment

Industrial metals are now ubiquitous within the atmosphere and their deposition represents a potential source of contamination to surficial environments. Few studies, however, have examined the environmental fate of atmospheric industrial metals within different surface environments. In this study, patterns of accumulation of atmospherically transported industrial metals were investigated within the surface environments of the Snowy Mountains, Australia. Metals, including Pb, Sb, Cr and Mo, were enriched in aerosols collected in the Snowy Mountains by 3.5–50 times pre-industrial concentrations. In sedimentary environments (soils, lakes and reservoirs) metals showed varying degrees of enrichment. Differences were attributed to the relative degree of atmospheric input, metal sensitivity to enrichment, catchment area and metal behaviour following deposition. In settings where atmospheric deposition dominated (ombrotrophic peat mires in the upper parts of catchments), metal enrichment patterns most closely resembled those in collected aerosols. However, even in these environments significant dilution (by 5–7 times) occurred. The most sensitive industrial metals (those with the lowest natural concentration; Cd, Ag, Sb and Mo) were enriched throughout the studied environments. However, in alpine tarn-lakes no other metals were enriched, due to the dilution of pollutant-metals by catchment derived sediment. In reservoirs, which were located lower within catchments, industrial metals exhibited more complex patterns. Particle reactive metals (e.g. Pb) displayed little enrichment, implying that they were retained up catchment, whereas more soluble metals (e.g., Cu and Zn) showed evidence of concentration. These same metals (Cu and Zn) were depleted in soils, implying that they are preferentially transported through catchments. Enrichment of other metals (e.g. Cd) varied between reservoirs as a function of contributing catchment area. Overall this study showed that the fate of atmospherically derived metals is complex, and depends upon metal behaviour and geomorphic processes operating at landscape scales.

Analytical solution of a kinematic wave approximation for channel routing

The kinematic wave approach is often used in hydrological models to describe channel and overland flow. The kinematic wave is suitable for situations where the local and convective acceleration, as well as the pressure term in the dynamic wave model is negligible with respect to the friction and body forces. This is the case when describing runoff processes in the upper parts of catchments, where slopes are generally of the order of 10−3. In physical-based hydrological models, the point-scale conservation equations are integrated over model entities, such as grid pixels or control volumes. The integration leads to a set of ordinary differential governing equations, which can be solved numerically by methods such as the Runge–Kutta integrator. Here, we propose an analytical solution of a Taylor-series approximation of the kinematic wave equation, which is presented as non-linear reservoir equation. We show that the analytical solution is numerically robust and third-order accurate. It is compared with the numerical solution and the solution of the complete dynamic wave model. The analytical solution proves to be computationally better performing and more accurate than the numerical solution. The proposed analytical solution can also be generalized to situations of leaking channels.

Significance of paleovalley sediments and landscape in the development of stream salinity in three southwest Australian catchments

Cenozoic fluvial sediments present west of the Meckering Line occur at similar elevation ranges (mostly 200–260 m AHD) in the largely rejuvenated forested landscapes of the Darling Plateau between the Helena River catchment and the south coast of Western Australia. These widespread paleovalley sediments are more continuous than previously recognised, and possess common hydrogeological characteristics. The upper parts of catchments in southwest Western Australia are flat and poorly drained with widespread salt lakes and wetland systems developed on the sediments. The lower rejuvenated landscapes below the base of remnant sediments, which are locally marked by saline springs and right angle changes in river courses, have undulating topography with well-defined drainage lines cut into competent basement rocks. This paper identifies groundwater flow systems associated with the paleovalley sediments in three varied catchments and describes the role of the Cenozoic sand aquifer in the development and potential management of dryland salinity. Groundwater flow in the Cenozoic paleovalley sand aquifer has more significance for land and water salinisation than that in the local weathered basement. The sand aquifer is a conduit for salt mobilised from weathered basement following land clearing. Erosion of the sedimentary profile by rejuvenation has exposed this sand aquifer within specific elevation ranges in modern drainages facilitating saline groundwater discharge, and land and water salinisation. In the Helena River catchment 63% of the salt load to the Mundaring Reservoir is discharged through this sand aquifer in only 30% of the streamflow. Such mismatched salt load and flow means southwest landscapes respond differently to key dryland and stream salinity management actions. Revegetation to reduce the salt load should target areas of weathered basement locally discharging saline groundwater to the sand aquifer. Reforestation elsewhere in the rejuvenated bedrock landscape can, by contrast, reduce the streamflow (that is diluting large salt loads from the remnant sedimentary landscapes) and hence raise the overall stream salinity.

Sediment concentration changes in runoff pathways from a forest road network and the resultant spatial pattern of catchment connectivity

Hydrological connectivity is a term often used to describe the internal linkages between runoff and sediment generation in upper parts of catchments and the receiving waters. In this paper, we identify two types of connectivity: direct connectivity via new channels or gullies, and diffuse connectivity as surface runoff reaches the stream network via overland flow pathways. Using a forest road network as an example of a landscape element with a high runoff source strength, we demonstrate the spatial distribution of these two types of linkages in a 57 km 2 catchment in southeastern Australia. Field surveys and empirical modelling indicate that direct connectivity occurs primarily due to gully development at road culverts, where the average sediment transport distance is 89 m below the road outlet. The majority of road outlets were characterised by dispersive flow pathways where the maximum potential sediment transport distance is measured as the available hillslope length below the road outlet. This length has a mean value of 120 m for this catchment. Reductions in sediment concentration in runoff plumes from both pathways are modelled using an exponential decay function and data derived from large rainfall simulator experiments in the catchment. The concept of the volume to breakthrough is used to model the potential delivery of runoff from dispersive pathways. Of the surveyed road drains ( n=218), only 11 are predicted to deliver runoff to a stream and the greatest contributor of runoff occurs at a stream crossing where a road segment discharges directly into the stream. The methodology described here can be used to assess the spatial distribution and likely impact of dispersive and gullied pathways on in-stream water quality.