Nilgiris is an important catchment area for several perennial rivers including the Cauvery and Bhavani, on which, large human populations are dependent downstream. The natural vegetation in the Nilgiris is a mosaic of high-altitude grasslands and forests, which helps in interception and retention of rainwater and thereby regulates water-flow in the streams and rivers throughout the year. However, these natural vegetation are facing a threat of invasion by exotic plants, such as wattles and woody shrubs like broom grasses and gorse, which can affect ecosystem processes and services. Exotic tree species, have invaded natural grasslands in the Nilgiris. Our earlier study in this landscape clearly showed the impacts of the invasives on stream-flows and run-off. However, the hydrological responses varied with the density of invasive cover. Building on our earlier findings, in this study, we will monitor and generate baseline data on stream-flows, run-off, evapotranspiration, and soil-properties across catchments with different levels of invasive species coverage. We will provide benchmark data on ecosystem function indicators and physical condition indicators at reference grassland sites which would help in assessing the impact of wattle invasion and for monitoring the success of grassland restoration activities in the future.