NEGOTIATIONS
FOCUS
PROCESS
KEY STEPS
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Compendium on methods and tools to evaluate impacts of, and vulnerability and adaptation to, climate
change
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ACRU (Agricultural Catchments Research Unit)
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Description
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The ACRU model has its origins in a catchment evapotranspiration based study carried out in
Natal in the early 1970s. The agrohydrological component of ACRU first came to the fore
during research on an agrohydrological and agroclimatological atlas for Natal.
ACRU is a multipurpose model that integrates water budgeting and runoff components of the
terrestrial hydrological system with risk analysis, and can be applied in crop yield
modeling, design hydrology, reservoir yield simulation and irrigation water demand/supply,
regional water resources assessment, planning optimum water resource allocation and
utilization, climate change, land use and management impacts, and resolving conflicting
demands on water resources.
The ACRU model uses daily multilayer soil water budgeting and has been developed essentially
into a versatile total evaporation model. It has therefore been structured to be highly
sensitive to climate and to land cover/use changes on the soil water and runoff regimes, and
its water budget is responsive to supplementary watering by irrigation, to changes in tillage
practices, or to the onset and degree of plant stress.
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Appropriate Use
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ACRU can be used at the catchment or subcatchment level to study the impact of climate change
and enhanced CO2 conditions on crop yield and water balances.
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Scope
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ACRU can operate as site-specific or as a lumped small catchments model. However, for large
catchments or in areas of complex land uses and soils, ACRU can operate as a distributed
cell-type model.
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Key Output
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Crop yield and water balances (including irrigation needs, runoff, etc.) for different climate
change scenarios.
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Key Input
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Weather data: maximum and minimum temperatures, rainfall. Catchment: location, area,
configuration, altitude. Other data: land cover, soil properties (texture, depth).
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Ease of Use
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For trained hydrologists and agronomists.
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Training Required
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No formal training required, but advanced knowledge of plant and soil processes as well as
hydrology is needed.
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Training Available
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Training and support is available from the School of Bioresources Engineering and Environmental
Hydrology, University of Natal, Pietermaritzburg, South Africa.
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Computer Requirements
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Windows-based PC
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Documentation
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Smithers, J. and R. Schulze. 1995. ACRU: Hydrological Modelling System. User Manual Version 3.
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Applications
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ACRU has been used to assess the potential impact of elevated CO2 and temperature levels and
possible changes in precipitation and potential evaporation on crop and runoff production in
southern Africa. The model has also been used to study shifts in maize production regions in
southern Africa as a consequence of global climate change. A version of ACR linked to the CERES
Maize model was used to simulate possible changes in maize production under different
fertilizer scenarios over southern Africa.
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Contacts for Framework, Documentation, Technical Assistance
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Roland E Schulze
School of Bioresources Engineering and Environmental Hydrology, University of Natal, Private
Bag X01, Scottsville 3209, Pietermaritzburg, South Africa; Tel: 033.260.5490; e-mail:
schulzer@nu.ac.za
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Cost
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Not identified
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References
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Schulze, R.E., G. Kiker, and R.P. Kunz. 1993. Global climate-change and agricultural
productivity in Southern Africa. Global Environmental Change 3:330-349.
Schulze, R. 1989. ACRU: Background, Concepts and Theory. Report 35, Agricultural Catchments
Research Unit, Department of Agricultural Engineering, University of Natal, Pietermaritzburg,
South Africa.
Tarboton, K.C. and R.E. Schulze. 1991. The ACRU modeling system for large catchment water
resources management. Int. Assoc. Hydrol. Sci. Publ. 201:219-232.
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