In the fields of agricultural and forest water use and water management, the CSIR has skills in the detailed quantification of crop and tree water-use, agrometeorology and surface water- groundwater interactions. Through the combination of these skills, researchers have gained experienced in the measurement and modelling of plant water-use and growth, irrigation-use efficiencies in agricultural crops (‘crop per drop’ ), the water-use efficiencies of trees (including fruit tree crops, indigenous and introduced tree species, and alien invasive plants), and the hydrological impacts of agricultural and forestry land-use.

South Africa faces water resource challenges of increasing water scarcity and competition for water due to population expansion, economic growth, climate change and deteriorating water quality. The country needs to improve its water productivity and reduce the non-beneficial use of water. This is particularly important in the irrigated agriculture and forestry sectors of South Africa to which approximately two thirds of the surface water resources of the country have been allocated.

Dependence on irrigation for the production of key crops such as vegetables and fruit is substantial due to low, erratic or unreliable rainfall in many parts of the country, combined with the high value (export potential) of those crops. However, there is essentially no more water available to allocate to irrigation. Consequently, we have to improve knowledge on crop water requirements and associated irrigation scheduling, thereby enhancing water productivity (crop yield produced per unit of water used). Furthermore, while plantation forestry in South Africa is critical for timber and fibre production, income generation and job provision, it comes at an environmental cost, notably an impact on water resources. The ongoing spread of invasive alien plant species also reduces water availability in the country.

A number of research projects conducted by the CSIR have quantified water-related impacts associated with irrigation, plantation forestry and invasive alien plants. Researchers quantify the water use of different agricultural and tree/forest land cover. Techniques include in-field vegetation water use monitoring, remote sensing/earth observation to quantify spatial evapotranspiration patterns, crop and tree water use modelling, and application of agricultural water use impact indices and tools such as water use efficiency/water productivity, water footprints and life cycle analysis. The potential impact and applications of this information are important at scales ranging from on-farm irrigation scheduling to catchment water resources management.