Estimation of groundwater recharge rate considering natural and artificial factors at a coastal area in the Busan City

Abstract

In this study, the actual evapotranspiration was estimated according to use and climate change in a coastal area, and the relationship between actual evapotranspiration meteorological factors was analyzed. The groundwater recharge was estimated by considering the runoff, water supply？Esewer rate, groundwater use (livelihood, industry, agriculture and others) and subway and electronic cable tunnel outflow rate. Sugyeong River to the east is located and Mt. Kuumryun to the west is bounded. Sugyeong Bay is formed to the south, and Mt. Bae is bounded to the north. The actual evapotranspiration was estimated by using potential evapotranspiration, precipitation and the plant-available water coefficient. Parameters to estimating the potential evapotranspiarion are the mean daily air temperature, dewpoint temperature, atmospheric pressure and mean wind speed. In 2002, the actual evapotranspiration was the highest (554.14 mm/yr), and it was the lowest in 2003 (427.91 mm/yr). The fluctuation of the potential evapotranspiration and actual evapotranspiration was similar. Correlations analysis between the evapotranspiration and the meteorological factors were performed. The correlation coefficient of the actual evapotranspiration and potential evapotranspiration was 0.96, high, but the correlation coefficient of 1) the precipitation and actual evapotranspiration; 2) the precipitation and potential evapotranspiration were very low, respectively. The influence of the potential and actual evapotranspiration and the mean wind speed was higher than others, and the correlation coefficients were 0.73 and 0.67. The evapotranspiration in the coastal urban areas is caused predominantly by wind speed than meteorological factors such as precipitation and temperature. Runoff was 49.80 % of the precipitation because increasing impermeable layer (building, road and so on) according to urbanization. Groundwater usage, leakage of water supply？Esewage, groundwater discharge from subway and electronic cable tunnel were considered to estimate groundwater recharge. Influence for the sustainable development yield came next with the precipitation, runoff and evapotranspiration. It is because precipitation cannot infiltrated into underground in the large areas having w=0 (building, road, others). In order to use, conservation and management of groundwater, they should be considered the exact value of each factor because natural factors (evapotranspiration, baseflow, coastal flow) and artificial factors (runoff, groundwater use, leakage of water supply？Esewage, groundwater discharge from subway and electronic cable tunnel) to estimate accurate values.