Long-term Spatially Distributed Solutional Erosion: How Do We Put Solutes on the Map?

Abstract

Much of the short-term solute process research in the last 20 years has focused on hydrochemical behaviour. This can help with the identification of solute source area type, but not the actual location of the solutional loss. The location and the spatial distribution of erosion are crucial to the identification of long-term landscape evolution. The way ahead lies in the fact that catchment budgeting and geochemical studies have been able to provide solute uptake rates. If these can be related to soil type, through a knowledge of soil mineralogy, reactive surface area and water flow rate, it may be possible to characterize the location and spatial distribution of solutional erosion through terrain analysis and soil maps in a geographical information system.

Chemical weathering and runoff chemistry in a steep headwater catchment

“…Water balance suggests that the residence time of water in the catchment is about 2 months, and that typical 24 h storms displace only a fraction of the stored water. A consequence is that runoff chemistry is dominated by old water, which imposes strong limits on the variability of runoff composition.to draw conclusions about the rate of chemical denudation, the processes of soil formation and the temporal evolution of runoff chemistry.Catchment studies of weathering have generally focused on weathering rates within the catchment as a whole, rather than identifying where in the catchment the processes occur (Drever and Clow, 1995;Trudgill and Wise, 1997). In a seminal analysis of weathering processes in the Sierra Nevada, Garrels and Mackenzie (1967) compared weathering in ephemeral springs, representing shallow, short-contact paths, with perennial springs, representing deep, long-contact time paths.…”

“…Catchment studies of weathering have generally focused on weathering rates within the catchment as a whole, rather than identifying where in the catchment the processes occur (Drever and Clow, 1995;Trudgill and Wise, 1997). In a seminal analysis of weathering processes in the Sierra Nevada, Garrels and Mackenzie (1967) compared weathering in ephemeral springs, representing shallow, short-contact paths, with perennial springs, representing deep, long-contact time paths.…”

Simulating loss of primary silicate minerals from soil due to long-term weathering using Allogen: Comparison with soil chronosequence, lake sediment and river solute flux data

“…This is straightforward enough for a specified soil profile, but it is not obvious how to determine the soil thickness appropriate for a given region. Indeed, it is not entirely straightforward to define soil thickness; certainly nothing in the water quality data tells us where in the vertical profile of a hillslope the weathering takes place (Trudgill and Wise, 1997). In effect, the model treats soil thickness as a measure of spatially averaged cumulative mineral surface area, the soil contributing so much more to this than the much thicker underlying bedrock that the latter can be neglected, an assumption broadly supported by observation that surface waters are similar to soil waters (White, 1995).…”