Monitoring water quality and modeling water balance and soil loss in Nonoc watershed in Surigao del Norte [Philippines]

Results of the physicochemical properties of the water collected varied from station to station which sometimes exceeded the established limits. Heavy metals in the water such as chromium, nickel, and iron were unusually high which can be traced to the natural occuring phenomena being a mining reserve area. Bacteriological analyses of the drinking water showed that they were contaminated with E. coli, fecal coliform and total coliform. Only 20 percent of the ten stations monitored were considered safe from bacteriological contamination. A total of 21 species of phytoplankton was identified during three sampling regimes with December sampling as the most diverse. Zooplankton was not abundant and their diversity was low. The macroinvertebrates, on the other hand, consisted of freshwater shrimps (Macrobrachium sp.) and a few types of insects such as the beetles and dragonflies. There was the absence of whole bodies of benthic organisms in the creek beds. Nonoc watershed received 243.81 cm of measured rainfall during the study period. Simulation results showed that 21 percent of the rainfall went to surface runoff, 22 percent of actual evapotranspiration and 57 percent to infiltration. From the overall water balance, the watershed has enough water surplus from rainfall to feed the creeks and groundwater systems in the whole river basin. Simulation results on soil erosion caused by surface runoff in the watershed showed that Bare/Mine-Out area lost 6.2 x 10 E4 tons or 1.57 cm of topsoil which can be categorized as very high or very severe erosion while forested scrubs lost 0.79 cm of topsoil equivalent to 2.5 x 10 E5 tons and open scrubs also lost 0.74 cm of topsoil with a total of 9.9 x 10 E4 tons which can be categorized as high or severe erosion. Soil loss thru erosion in the watershed ranged from low erosion to very high or very severe erosion. Bare/Mine-out, Forested, and Open scrubs are among the land use classification in the watershed that are considered as potential sources of nonpoint environmental pollutants. The high soil loss rate is a cause for concern since surface water downstream and around the watershed are the receiving ends of the sediments carried by runoff