Change Anomalies of Hydrologic Responses to Climate Variability and Land-use Changes in the Mt. Makiling Forest Reserve

Climate variability leads to direct impact on hydrology on a watershed, but the response to future climate condition may vary with land use and cover. The study assessed the change anomalies of hydrologic system (streamflow, evaporation, and seepage) using two CGCM3 scenarios (A1B and A2 climate scenarios) in the four different land covers responding for specific periods of 2020s, 2050s, and 2080s in the Mt. Makiling Forest Reserve, Philippines. The BROOK90 hydrologic model was employed with projected climate scenarios. Results indicated similar patterns of streamflow and seepage variations in forest and managed agroforestry land uses while changes in evaporation rates were found highly significant in A1B and A2 climate scenarios. Change anomalies in a cultivated agroforestry area showed higher streamflow discharge and seepage losses than other land uses while evaporation rates were insignificantly different in two scenarios under certain periods. Outcomes emerged to be most severe in the special-use area, which ascertained to the increasing annual streamflow (12-36%), decreasing evaporation (1-4%), and increasing seepage losses (10-25%) in the near future. Overall, impacts of climate change based on predicted CGCM3 climate scenarios in hydrologic system established significant fluctuations for three time intervals regardless of land cover.