Estimating Base Flow Index to Predict Soil Permeability

Abstract

Predicting Base Flow Index (BFI) in catchments area is important especially for the management of water resources, specifically for developing integration between surface water and groundwater. BFI can be used to determine the characteristic and movement of groundwater flow, even the World Meteorological Organization (WMO) in 2008 used BFI as an indicator to determine soil permeability and groundwater availability in catchments. Some existing researches only estimate two option values, namely high BFI with permeable conditions and low BFI with impermeable conditions. The purpose of this study is to find the relationship between several soil permeability values and soil types from various BFI values that are more detailed in a catchment. Base Flow Index (BFI) is the ratio of base flow and total streamflow. Base flow is estimated by the hydrograph separation method including BFI Standard (The United Kingdom Institute of Hydrology), HYSEP and PART using The USGS (United State Geological Survey) computer program-Groundwater Toolbox version 1.0 with data on daily streamflow for five years (2011-2015). The PART method is chosen because it has a linear correlation with base flow with streamflow and base flow with annual average rainfall with the highest R2. The soil permeability range of analysis result is greater than the soil permeability in study area. It indicates that the base flow estimation using the hydrograph separation method can be conducted because there is an overestimate in determining the base flow.