Predicting impacts of land use changes on catchment hydrological processes

Journal papers

Karvonen, T., Koivusalo, H., Jauhiainen, M., Palko, J. and Weppling, K. 1999. A hydrological model for predicting runoff from different land use areas, Journal of Hydrology, 217(3-4), 253-265. [abstract]

Koivusalo, H. and Heikinheimo, M. 1999. Surface energy exchange over a boreal snowpack: comparison of two snow energy balance models, Hydrological Processes, Vol 13(14-15), 2395-2408. [abstract]

Koivusalo, H., Karvonen, T. and Lepistö, A. 2000. A Quasi-Three-Dimensional Model for Predicting Rainfall-Runoff Processes in A Forested Catchment in Southern Finland, Hydrology and Earth System Sciences, 4(1), 65-78. [abstract]

Koivusalo, H., Karvonen, T. and Paasonen-Kivekäs, M. 1999. Application of a two-dimensional model to calculate water balance of an agricultural hillslope, Physics and Chemistry of the Earth (B), 24(4), 313-318. [abstract]

Kokkonen, T., Koivusalo, H. and Karvonen, T. 2001. A semi-distributed approach to rainfall-runoff modelling - a case study in a snow affected catchment. Environmental Modelling & Software (in press). [abstract]

Submitted manuscripts

Koivusalo, H. and Kokkonen, T. 2000. Snow processes in a forest clearing and in a coniferous forest. Journal of Hydrology (submitted). [abstract]

Koivusalo H. and Kokkonen, T. 2001. Modelling Runoff Generation in a Forested Catchment in Southern Finland. Hydrological Processes (submitted). [abstract]

Conference papers

Koivusalo, H., Jauhiainen, M., & Karvonen, T. 1998. Use of characteristic hillslopes to model hydrological effects of land use change in forested areas. XX Nordic Hydrological Conference, Helsinki 10-13 August 1998. In: Kajander, J. NHP Report 44(2). pp. 522-532

Koivusalo, H., Kokkonen, T. & Karvonen, T. 2000. Modeling runoff generation in a forested catchment in Southern Finland. International Workshop, 9-12 Oct 2000, Freiburg i. Br., Germany. In: Leibundgut, C., Uhlenbrook, S. & McDonnell, J. Runoff Generation and Implications for River Basin Modelling. Albert-Ludwigs-Universität Freiburg. pp. 28-29.

Koivusalo, H., Paasonen-Kivekäs, M. Karvonen, T. & Vakkilainen, P. 1999. Water and nitrogen balance on a cultivated field: a characteristic hillslope approach. IUGG 99 Symposium, Birmingham, UK, July 1999. In: Heathwaite, L. Impact of Land-Use Change on Nutrient Loads from Diffuse Sources. IAHS. No. 257, pp. 157-162

Lundberg, A. & Koivusalo, H. 2000. Use of operational snow course measurements to approximate snow interception evaporation. XXI Nordic Hydrological Conference, Uppsala, Sweden, 26-30 June 2000. In: Nilsson, T. NHP Report No 46. Vol. 2, pp. 570-577.

Paasonen-Kivekäs, M., Koivusalo, H., Karvonen, T., Vakkilainen, P. and Virtanen, J. 1999. Nitrogen transport via surface and subsurface flow in an agricultural field. IUGG 99 Symposium, Birmingham, UK, July 1999. In: Heathwaite, L. Impact of Land-Use Change on Nutrient Loads from Diffuse Sources. IAHS. No. 257, pp. 163-169.

Conference abstracts

Koivusalo, H., Karvonen, T., Kokkonen, T. & Lepistö, A. 2000. Modeling runoff generation and water flow pathways in a small forested catchment. XXV European Geophysical Society General Assembly, Nice, April 2000. Geophysical Research Abstracts. Vol. 2,

Koivusalo, H., Karvonen, T., & Paasonen-Kivekäs, M. 1997. Application of a two-dimensional model to calculate water balance of an agricultural hillslope. XXII European Geophysical Society General Assembly, Vienna, Austria, April 1997. Annales Geophysicae. EGS. Supplement II to Volume 15, p. C337.

Koivusalo, H., Kokkonen, T. & Karvonen, T. 2000. Modeling runoff generation in a forested catchment in Southern Finland. International Workshop, 9-12 Oct 2000, Freiburg i. Br., Germany. In: Leibundgut, Ch., Uhlenbrook, S. & McDonnell, J. Runoff Generation and Implications for River Basin Modelling. Albert-Ludwigs-Universität Freiburg; 28-29.

Other publications

Koivusalo, H. 1997. Hillslope Hydrological Processes - Surface Runoff and Snowmelt on an Agricultural Field, Licentiate's Thesis, Department of Civil and Environmental Engineering, Helsinki University of Technology, 60+142 p.

Koivusalo, H., Kokkonen, T. & Karvonen, T. 2000. Modeling runoff from hydrologically similar areas, Book Chapter Submitted to Watershed Modeling, (ed. by V.P. Singh).

Selected abstracts

Karvonen, T., Koivusalo, H., Jauhiainen, M., Palko, J. and Weppling, K. 1999. A hydrological model for predicting runoff from different land use areas, Journal of Hydrology, 217(3-4), 253-265.

Abstract

The purpose of this paper is to model the influence of land use on catchment runoff. The modeling is based on the sub-division of the catchment into smaller units by generation of so-called "hydrologically similar units" (HSU) or "patch types". HSUs aggregate areas of hydro-logically similar behaviour, e.g., land use, soil, slope, and vegetation. Each HSU is represented using a cross-section called a "characteristic profi-le". For the calculation of the water balance of the characteristic profiles, mathematical treatment of the key partitions of the hydrograph response has been developed. The characteristic profile is the largest unit that can be handled mathematically still maintaining the idea of a hydrologically similar regime. An agricultural characteristic profile is a cross-section between two parallel open ditches or subsurface drains. For forest areas the characteristic profile is called hillslope and the length of the hillslope can vary from few meters up to hundreds of meters. Total runoff from the characteristic profiles is an input to a channel network. In the present model, the channel processes are described using the geomorphologic instantaneous unit hydrograph (GIUH). The proposed hydrological model was tested in the Lestijoki catchment (1290 km2) located in the western Finland. The catchment was subdivided into 25 characteristic profiles with parameters fixed to typical values measured in Finnish conditions. The model calibration was carried out for the GIUH parameters using measured daily river flow. The coefficient of determination was 0.74 for a two-year calibration period, and 0.70 for a three-year testing period. The model represented well the extent of variable contributing areas, which was the main reason for the non-linear behaviour of the catchment response.

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Koivusalo, H. and Heikinheimo, M. 1999. Surface energy exchange over a boreal snowpack: comparison of two snow energy balance models, Hydrological Processes, Vol 13(14-15), 2395-2408.

Abstract

The objective was to compare two energy balance models to simulate energy exchange, skin temperature and albedo at the snow surface. Point measurements of vertical snow temperature and density profiles, snow surface temperature, net radiation and albedo were taken during spring 1997 at a site within a sparse coniferous stand in Northern Finland. Standard meteorological measurements were available near the snow site at the Sodankylä Meteorological Observatory. The study period included two weeks of measurements of turbulent heat fluxes with the eddy-correlation method above snow as a part of the NOPEX-WINTEX project "Land-surface-atmosphere interactions in a wintertime boreal landscape". Two point models with different snow process representations were tested and the modeled energy fluxes at the snow surface were compared. UEB (Tarboton and Luce, 1996) was chosen as a simple model, which derived the surface energy fluxes but treated the snowpack as one layer. SNTHERM (Jordan, 1991) represented a sophisticated model to simulate mass and energy transfer at the snowpack boundaries and within the snow cover. The results showed major differences in the modeled radiation balance due to different albedo procedures implemented in the models. The model comparison using identical radiation input data indicated that SNTHERM had a better overall agreement to the measurements as compared with UEB. Major differences between the two models were found in the calculation of sensible heat flux and snow surface temperature, which were sensitive to the correction for atmospheric stability and snow thermal conductivity, respectively. The comparison of the SNTHERM results to the eddy-correlation measurements of sensible heat flux supported the use of a restricted correction for atmospheric stability. The forest canopy had a notable effect on the short-wave radiation balance, the vertical wind profile, and the measured sensible heat flux.

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Koivusalo, H., Karvonen, T. and Lepistö, A. 2000. A Quasi-Three-Dimensional Model for Predicting Rainfall-Runoff Processes in A Forested Catchment in Southern Finland, Hydrology and Earth System Sciences, 4(1), 65-78.

Abstract

Runoff generation in a forested catchment (0.18 km2) was simulated using a quasi-three-dimensional rainfall-runoff model. The model was formulated over a finite grid where water movement was assumed to be dominantly vertical in the unsaturated soil zone and horizontal in the saturated soil. The vertical soil moisture distribution at each grid cell was calculated using a conceptual approximation to the one-dimensional Richards equation. The approximation allowed the use of a simple soil surface boundary condition and an efficient solution to the water table elevation over the finite grid. The approximation was coupled with a two-dimensional ground water model to calculate lateral soil water movement between the grid cells and exfiltration over saturated areas, where runoff was produced by the saturation-excess mechanism. Runoff was an input to a channel network, which was modeled as a non-linear reservoir. The proposed approximation for the vertical soil moisture distribution in unsaturated soil compared well to a numerical solution of the Richards equation during shallow water table conditions, but was less satisfactory during prolonged dry periods. The simulation of daily catchment outflow was successful with the exception of underprediction of extremely high peak flows. The calculated water table depth compared satisfactorily with the measurements. An overall comparison with the earlier results of tracer studies indicated that the modeled contribution of direct rainfall/snowmelt in streamflow was higher than the isotopically traced fraction of event water in runoff. The seasonal variation in the modeled runoff-contributing areas was similar to that in the event water-contributing areas from the tracer analysis.

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Koivusalo, H., Karvonen, T. and Paasonen-Kivekäs, M. 1999. Application of a two-dimensional model to calculate water balance of an agricultural hillslope, Physics and Chemistry of the Earth (B), 24(4), 313-318.

Abstract

The objective was to simulate runoff production on an agricultural hillslope in Southern Finland. Water balance was calculated using a quasi-two-dimensional model describing vertical soil moisture distribution and horizontal water movement along a hillslope strip. The model accounted for the production of saturated overland flow on the exfiltration part of the hillslope. The model results were assessed against measurements of surface runoff, subsurface drainage flow, and water table level, which were available at individual field sections for years 1995-96. Intensive runoff events during summer and autumn rainfalls were the primary focus in the modeling application. The model performed well during wet periods when water table remained close to the soil surface, but the results were less satisfactory during dry periods.

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Kokkonen, T., Koivusalo, H. and Karvonen, T. 2001. A semi-distributed approach to rainfall-runoff modelling - a case study in a snow affected catchment. Environmental Modelling & Software (in press). Individual components of cycle

Abstract

A semi-distributed hydrological model was applied to a small forested catcment in southern Finland. The aim was to demonstrate how differences in terrain properties could be taken into account in modelling runoff generation, and to test how well the presented model simulated streamflow with only limited calibration. Modelling was based on subdivision of a catchment into topographically similar areas, which were identified from a digital elevation model. The water balance in each area was calculated using a hillslope-scale model. Discharges from the set of hillsope-scale models were combined with the aid of a routing procedure to yield the total streamflow at the catchment outlet. The catchment receives approximately 30 per cent of the annual precipitation as snow, and thus a snow model was required in winter periods. The presented semi-distributed model was capable of reproducing fairly well the measured streamflow when only two model parameters were calibrated against streamflow. The results suggested that unlike the cumulative runoff, the temporal variability of runoff response was affected by terrain topography. Only minor differences were detected in reproduction of streamflow between the semi-distributed model and a simple lumped model IHACRES used as a reference.

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Koivusalo, H. and Kokkonen, T. 2000. Snow processes in a forest clearing and in a coniferous forest. Journal of Hydrology (submitted).

Abstract

An energy balance approach is applied to simulate snow accumulation and melt in a forest clearing and in a coniferous forest. The study site is located in southern Finland (60.1 N) where the winters are mild considering the high latitude. For forest simulations the snow model is coupled with a procedure, which accounts for the effects of the canopy on the driving meteorological variables of the snow model. Model results are first validated against measured values of snow water equivalent and snow temperature in a forested site and in an adjacent clearing. Subsequently differences in snow accumulation, snowmelt, and in energy components contributing to snowmelt in open and forested conditions are studied. Effect of the canopy on snow mass balance on the ground can be seen as higher accumulation and more intense snowmelt in the open. Due to these counteracting processes the results show little difference in the annual maximum of the snow water equivalent in the clearing and in the forest. In mid-winter the main source of energy for snowmelt is sensible heat in the open, whereas both sensible heat and net radiation contribute equally to snowmelt in the forest. Solar radiation intensity increases towards the spring, which causes net radiation to become dominant in both sites.

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Koivusalo H. and Kokkonen, T. 2001. Modelling Runoff Generation in a Forested Catchment in Southern Finland. Hydrological Processes (submitted).

Abstract

Runoff generation in a forested catchment (0.18 km2) was studied by comparing model simulations against measurements of groundwater levels and streamflow, and against separation of runoff components based on isotope tracer analysis. Runoff generation mechanisms within the catchment were modelled with aid of a single two-dimensional hillslope, which represents a typical flow strip from a water divide to a stream. The hydrological model used in this study had a physical basis, and it consisted of separate procedures for canopy, snow, and hillslope processes, and for routing in the channel network. This paper documents calibration and validation of the hillslope and routing procedures against groundwater levels and streamflow, respectively. Winter and summer seasons were examined separately in order to isolate different mechanisms controlling groundwater level behaviour. Based on groundwater level data, soil domain was split into two layers, and hydraulic properties of the layers and level of potential transpiration were adjusted. The results indicated that seasonal runoff dynamics could be replicated without calibration of the hillslope procedure against measured streamflow. The routing procedure could merely delay the runoff input it received from the hillslope procedure. Channel routing had no influence on how large a share of a throughfall/snowmelt event, under different preceding climatic conditions, eventually emerged as streamflow. Comparison against isotope tracer data suggested that use of groundwater level measurements in the model calibration could lead to a more plausible simulation of new and old water contributions to streamflow. Still, the modelled new water fraction in streamflow was nearly twice as large as the fraction derived from isotope tracer analysis. Improvement of the model structure towards a more realistic separation of runoff components would require the model to consider residence times of water in different parts of the soil domain.

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Contents

• Overview
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• Presentation
• Publications