Journal of Hydrology (NZ) 47 (2): 67-84 2008 © New Zealand Hydrological Society (2008) Hydrological impacts of irrigated agriculture in the Manuherikia catchment, Otago, New Zealand Stefan W. Kienzle1 and Jochen Schmidt2 1 Department of Geography, University of Lethbridge, Alberta, Canada 2 National Institute of Water and Atmospheric Research, P.O. Box 8602, Christchurch, New Zealand. Corresponding author:
[email protected] Abstract to losses in the conveyance system, on Water for irrigation is becoming an in farm application losses, increased actual creasingly critical component of New evapotranspiration, and the development of Zealand’s rural economy. Projections of a deeper rooting system compared to natural expanding agricultural sectors indicate vegetation. increased demands for water and a reliable water supply. Hence, it is pertinent to assess Introduction the impacts of water demand for current Water for irrigation is becoming an and future irrigated agriculture on catch increasingly critical component of New ment hydrology. This case study focuses Zealand’s rural economy. More intensive on estimating the hydrological impacts of farming systems are usually accompanied by irrigated agriculture in the Manuherikia a demand for increased water quantity and catchment upstream of Alexandra, Central a reliable water supply. Projections indicate Otago, New Zealand. In order to assess that New Zealand’s dairy, horticulture the impacts of irrigation on streamflow, and viticulture sectors will all expand in five landuse scenarios, including three the future, and it follows that there will be irrigation scenarios with varying efficiencies, growing demands for water for irrigated are investigated with the ACRU agro agriculture (Ministry of Agriculture and hydrological modeling system (Agricultural Forestry, 2004; Parliamentary Commissioner Catchments Research Unit (ACRU), for the Environment, 2004; Doak, 2005).