Abstract
Owing to urbanization, impervious areas within watersheds have continuously increased, distorting healthy water circulation systems by reducing soil infiltration and base flow; moreover, increases in surface runoff deteriorate water quality by increasing the inflow of nonpoint sources. In this study, we constructed a Hydrological Simulation Program—Fortran (HSPF) watershed model that applies the impervious area and can set medium- and long-term water circulation management goals for watershed sub-areas. The model was tested using a case study from the Yeongsan River watershed, Korea. The results show that impervious land-cover accounts for 18.47% of the upstream reach in which Gwangju City is located; approximately twice the average for the whole watershed. Depending on the impervious area reduction scenario, direct runoff and nonpoint source load could be reduced by up to 56% and 35%, respectively; the water circulation rate could be improved by up to 16%. Selecting management goals requires the consideration of both policy objectives and budget. For urban areas with large impervious cover, the designation of nonpoint source management areas is required. For new cities, it is necessary to introduce water circulation systems (e.g., low impact development techniques) to improve rainwater penetration and recharge and activate preemptive water circulation.
Highlights
Accepted: 29 July 2021Owing to advances in land use and an increase in economic activities, the impervious area has continuously increased in South Korea, rising to 7.7% in 2017 (2.6 times higher than in the 1970s)
An increase in the impervious area causes a reduction in soil penetration and base flow, which distorts the healthy water circulation system; increased surface runoff deteriorates water quality by increasing the inflow of nonpoint sources [4]
These analyses show the same trend as the result of increasing direct runoff and nonpoint source load according to the increase in impervious area suggested by [4]
Summary
Owing to advances in land use and an increase in economic activities, the impervious area has continuously increased in South Korea, rising to 7.7% in 2017 (2.6 times higher than in the 1970s). Studies have shown that the improvement of natural streams to expand urban areas increases the risk of flooding [6,7]. This issue is further exacerbated by unprecedented rainfall patterns and an increase in annual average temperature under the influence of climate change [1,8]. There is an increasing need to manage the impervious area
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