Hydrological Effects of Afforestation and Pasture Improvement in Montane Grasslands, South Island, New Zealand

Abstract

A paired catchment study was established at Glendhu Forest in 1979 in the southern South Island of New Zealand to assess the hydrological impacts of afforesting tussock grassland. After a 3-year calibration period (1980–1982) one catchment was planted in pines over 67% of its area and the other was left in tussock. By 1989 the difference in annual water yield from the planted catchment was 130 mm, and from 1991–1996 it averaged 270 mm (31% of total runoff from the control). Differences in low flows showed a similar trend, and suggest that in dry periods, afforestation of tussock grasslands can reduce water yields by 0.11 mm/day. Two examples of the application of these data to the resolution of local and regional resource management issues are discussed. They demonstrate the importance of long-term catchment monitoring programmes.Key wordshydrologyforestsgrasslandsafforestation