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Plynlimon research: The first two Decades, C. Kirby, M. D. Newson and K. Gilman (Eds), Institute of Hydrology, Report No. 109, 1991. No. of pages: 188. Price: £20.00. ISBN 0‐948540‐27‐3

Plynlimon research: The first two Decades, C. Kirby, M. D. Newson and K. Gilman (Eds), Institute... A. M. Roberts, J. A. Hudson and G. Roberts, Institute of Hydrology, Report No. 104,1990.No. of pages: 85. Price: f7.00. ISBN (3-948540-16-8 IMPACT O F CLIMATIC VARIABILITY AND CHANGE O N RIVER FLOW REGIMES IN THE UK, N. W. Arnell, R. P. C. Brown and N. S. Reynard, Institute of Hydrology, Report No. 107, 1990. No. of pages: 154. Price: E 12.00. ISBN (k-948540-26-5. PLYNLIMON RESEARCH: THE FIRST TWO DECADES, C. Kirby, M. D. Newson and K. Gilman (Eds), Institute of Hydrology, Report No. 109, 1991. No. of pages: 188. Price: €20.00. ISBN 0-948540-27-3. IMPACT O F IMPROVED LAND DRAINAGE O N RIVER FLOWS, M. Robinson, Institute of Hydrology, Report No. 113, 1990. No. of pages: 113. Price: E16.00. ISBN 0-94854Ck-24-9. This collection of recent Institute of Hydrology Reports presents a range of research focussing on external impacts on the hydrological system, in terms of both the quantity and quality of runoff. Three of them (Reports 104, 109 and 113) deal with the historic emphasis of much Institute research, namely the effects of changing land use and land use practices, while the fourth is concerned with the more topical and fashionable issue of climatic change. Taking them together allows the three to highlight the difficulties of the fourth, since it is clear that detecting the effect of quite significant land use change may require considerable experimental ingenuity, which argues against premature assumptions about the effects of changing climate. Report No. 104 summarizes a paired catchment study of pasture improvement in the Welsh uplands by direct drilling of grass seed which suggests that, at least with this minimum cultivation method, there is little effect on runoff quality (P, NH,-N) and sediment transport. It typifies concern with the quality of potable water supply in upland gathering grounds, the ‘treated‘ catchment draining into Nant-y-Moch reservoir. It also is typical in providing considerable detail of the measurement, sampling and interpolation methods used, differentiating this Report from journal articles, which rarely present sufficient detail on ‘Materials and Methods’ for genuine reproducible experimentation. However, this exposes a possible limitation, in that the sampling interval adopted may have been inadequate to characterize fully the flowrelated variability of the chemical determinants. Report No. 109 reviews a long-running paired catchment experiment designed to investigate the hydrological differences between upland grazing and coniferous forest, again in upland Wales, and again with a concern for impacts on water supply. Coniferous afforestation is shown to reduce streamflow, and increase hydrograph peakedness and erosion. This review of research illustrates both the considerable strengths and occasional limitations of Institute catchment studies. There is commendable emphasis on quality control in data acquisition, with consequent continual instrument development. The need for long-term study is clearly illustrated: by the perversity of British weather which allows a 20-year study to include two ‘100-year‘ floods, a ‘100-year’rainfall, and two ‘100-year’ droughts, variability which clearly demands a lengthy data collection period before trends are reliably identifiable; and by the lysimeter study of improved grassland reported on pages 13844 which still shows enhanced total nitrogen loading in drainage water after three years because of the initial effects of experimental disturbances. Although meticulous experimentation reveals the complex nature of the forest influence on water losses, by highlighting interception, the dominance of this empirical, experimental approach to hydrology is shown to have some limitations when on pages 170-1 a comparison with lowland eastern England shows that the effect of forest is reversed in a different regional context. The cost-effectiveness of this catchment research is best shown in the section on water chemistry (pages 124-31), which teases out an understanding of some hydrological processes; and might be further improved by the development of interactive experimental and modelling research as hinted at on pages 102-6. Without the process understanding and modelling capability which this Report is able to demonstrate, the resources locked up in a potentially site-specific catchment experiment are harder to justify. Report No. 113 nicely illustrates this general issue, showing through an extensive and rigorous review and compilation of experimental data that land drainage may either increase or decrease runoff depending on the initial character of the soil, and confirming this via computer modelling using the program DRAINMOD (Skaggs, 1980: North Carolina Agricultural Research Service, Technical Bulletin 267). Drainage of heavy clay soils reduces peak flows by preventing surface saturation, whereas drainage of loamy soils increases peak flows by accelerating subsurface flow. However, there remains a further complication, namely that conclusions deriving from analysis of field scale processes do not necessarily apply at the catchment scale, where in this case improvement of arterial drainage may submerge the effects of field drainage, or drains of very different ages and efficiencies may coexist. Thus in catchment regression models for time-to-peak or mean annual flood, the 0 1992 by John Wiley & Sons, Ltd. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Earth Surface Processes and Landforms Wiley

Plynlimon research: The first two Decades, C. Kirby, M. D. Newson and K. Gilman (Eds), Institute of Hydrology, Report No. 109, 1991. No. of pages: 188. Price: £20.00. ISBN 0‐948540‐27‐3

Earth Surface Processes and Landforms , Volume 17 (6) – Sep 1, 1992

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Publisher
Wiley
Copyright
Copyright © 1992 John Wiley & Sons, Ltd
ISSN
0197-9337
eISSN
1096-9837
DOI
10.1002/esp.3290170612
Publisher site
See Article on Publisher Site

Abstract

A. M. Roberts, J. A. Hudson and G. Roberts, Institute of Hydrology, Report No. 104,1990.No. of pages: 85. Price: f7.00. ISBN (3-948540-16-8 IMPACT O F CLIMATIC VARIABILITY AND CHANGE O N RIVER FLOW REGIMES IN THE UK, N. W. Arnell, R. P. C. Brown and N. S. Reynard, Institute of Hydrology, Report No. 107, 1990. No. of pages: 154. Price: E 12.00. ISBN (k-948540-26-5. PLYNLIMON RESEARCH: THE FIRST TWO DECADES, C. Kirby, M. D. Newson and K. Gilman (Eds), Institute of Hydrology, Report No. 109, 1991. No. of pages: 188. Price: €20.00. ISBN 0-948540-27-3. IMPACT O F IMPROVED LAND DRAINAGE O N RIVER FLOWS, M. Robinson, Institute of Hydrology, Report No. 113, 1990. No. of pages: 113. Price: E16.00. ISBN 0-94854Ck-24-9. This collection of recent Institute of Hydrology Reports presents a range of research focussing on external impacts on the hydrological system, in terms of both the quantity and quality of runoff. Three of them (Reports 104, 109 and 113) deal with the historic emphasis of much Institute research, namely the effects of changing land use and land use practices, while the fourth is concerned with the more topical and fashionable issue of climatic change. Taking them together allows the three to highlight the difficulties of the fourth, since it is clear that detecting the effect of quite significant land use change may require considerable experimental ingenuity, which argues against premature assumptions about the effects of changing climate. Report No. 104 summarizes a paired catchment study of pasture improvement in the Welsh uplands by direct drilling of grass seed which suggests that, at least with this minimum cultivation method, there is little effect on runoff quality (P, NH,-N) and sediment transport. It typifies concern with the quality of potable water supply in upland gathering grounds, the ‘treated‘ catchment draining into Nant-y-Moch reservoir. It also is typical in providing considerable detail of the measurement, sampling and interpolation methods used, differentiating this Report from journal articles, which rarely present sufficient detail on ‘Materials and Methods’ for genuine reproducible experimentation. However, this exposes a possible limitation, in that the sampling interval adopted may have been inadequate to characterize fully the flowrelated variability of the chemical determinants. Report No. 109 reviews a long-running paired catchment experiment designed to investigate the hydrological differences between upland grazing and coniferous forest, again in upland Wales, and again with a concern for impacts on water supply. Coniferous afforestation is shown to reduce streamflow, and increase hydrograph peakedness and erosion. This review of research illustrates both the considerable strengths and occasional limitations of Institute catchment studies. There is commendable emphasis on quality control in data acquisition, with consequent continual instrument development. The need for long-term study is clearly illustrated: by the perversity of British weather which allows a 20-year study to include two ‘100-year‘ floods, a ‘100-year’rainfall, and two ‘100-year’ droughts, variability which clearly demands a lengthy data collection period before trends are reliably identifiable; and by the lysimeter study of improved grassland reported on pages 13844 which still shows enhanced total nitrogen loading in drainage water after three years because of the initial effects of experimental disturbances. Although meticulous experimentation reveals the complex nature of the forest influence on water losses, by highlighting interception, the dominance of this empirical, experimental approach to hydrology is shown to have some limitations when on pages 170-1 a comparison with lowland eastern England shows that the effect of forest is reversed in a different regional context. The cost-effectiveness of this catchment research is best shown in the section on water chemistry (pages 124-31), which teases out an understanding of some hydrological processes; and might be further improved by the development of interactive experimental and modelling research as hinted at on pages 102-6. Without the process understanding and modelling capability which this Report is able to demonstrate, the resources locked up in a potentially site-specific catchment experiment are harder to justify. Report No. 113 nicely illustrates this general issue, showing through an extensive and rigorous review and compilation of experimental data that land drainage may either increase or decrease runoff depending on the initial character of the soil, and confirming this via computer modelling using the program DRAINMOD (Skaggs, 1980: North Carolina Agricultural Research Service, Technical Bulletin 267). Drainage of heavy clay soils reduces peak flows by preventing surface saturation, whereas drainage of loamy soils increases peak flows by accelerating subsurface flow. However, there remains a further complication, namely that conclusions deriving from analysis of field scale processes do not necessarily apply at the catchment scale, where in this case improvement of arterial drainage may submerge the effects of field drainage, or drains of very different ages and efficiencies may coexist. Thus in catchment regression models for time-to-peak or mean annual flood, the 0 1992 by John Wiley & Sons, Ltd.

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Published: Sep 1, 1992

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