RUNOFF AND HYDROLOGIC CHARACTERISTICS OF MAJOR RIVERS IN GENERAL SANTOS CITY: THE CASE OF SINAWAL RIVER

Barangay Sinawal is about 6,339.20 hectares, or about 11.8% of the total land area of General Santos City. QGIS estimates that the area covered by the Sinawal river basin is 6,981 hectares. It starts at the border of T'boli and flows through the barangays of Sinawal, Apopong, and Labangal.

This study was conducted in order to determine the Sinawal River's runoff and sediment discharge rate at its upstream, midstream, and downstream locations, as well as to determine basic surface water quality parameters like dissolved oxygen (DO), electrical conductivity, pH, temperature, total dissolved solids (TDS), total suspended solids (TSS), and turbidity, as well as analyze and recommend the river's current classification. The study set out to delineate and describe the watershed. The upstream, midstream, and downstream of the Sinawal river are located at 6°07'08" N, 125°6'0.8" E, 6°07'48.57" N, 125°06'42.58" E, and 6°06'41.67" N, 125°08'54.33" E, respectively. Upstream has the highest average discharge with 0.203 m3/s and it is located on the side of a small community that has been involved in human activities in the area. Where the contribution of human activities are small and some tributaries contribute, which is the reason for the increase in discharge.

With an average sediment concentration of 48.80 mg/L, midstream is the spot with the most sediment. It is located near the cabuay dressing plant and not far away, it also has a quarry and is surrounded by some locals. Because of various human activities, such as quarry extraction and some activities at the cabuay dressing plant, sediment contributes significantly to the water, which is why the sediment content has increased. As the river flows downstream, the sediment discharge rate increases. This water will flow through the barangays of Apopong and Labangal (downstream). Communities surrounding the river add sediment to the water, resulting in high sediment discharge.

Based on the obtained sample, the Sinawal River belongs to class C. The majority of physico-chemical water quality parameters that were monitored on-site complemented the classification obtained by the Department of Environment and Natural Resources.