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Compendium on methods and tools to evaluate impacts of, and vulnerability and adaptation to, climate change
ACRU (Agricultural Catchments Research Unit)

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.

Appropriate Use 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.
Scope 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.
Key Output Crop yield and water balances (including irrigation needs, runoff, etc.) for different climate change scenarios.
Key Input Weather data: maximum and minimum temperatures, rainfall. Catchment: location, area, configuration, altitude. Other data: land cover, soil properties (texture, depth).
Ease of Use For trained hydrologists and agronomists.
Training Required No formal training required, but advanced knowledge of plant and soil processes as well as hydrology is needed.
Training Available Training and support is available from the School of Bioresources Engineering and Environmental Hydrology, University of Natal, Pietermaritzburg, South Africa.
Computer Requirements Windows-based PC
Documentation Smithers, J. and R. Schulze. 1995. ACRU: Hydrological Modelling System. User Manual Version 3.
Applications 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.
Contacts for Framework, Documentation, Technical Assistance

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:

Cost Not identified

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.