Water cycle within the human civilization has become important with urbanization. To date, water cycle in the eco-system has been the focus in identifying the degree of water cycle in cities, but in practicality, water cycle within the human civilization system is taking on an increasing importance. While in recent years plans to reuse water have been implemented to restore water cycle in cities, the effect that such reuse has on the entire water cycle system has not been analyzed. The analysis on the effect that water reuse has on urban areas needs to be go beyond measuring the cost-savings and look at the changes brought about in the entire city’s water cycle system. This study uses a SWAT model and water balance analysis to review the effects that water reuse has on changes occurring in the urban water cycle system by linking the water cycle within the eco-system with that within the human civilization system. The SWAT model to calculate the components of water cycle in the human civilization system showed that similar to measured data, the daily changes and accumulative data can be simulated. When the amount of water reuse increases in urban areas, the surface outflow, amount of sewer discharge and the discharged amount from sewage treatment plants decrease, leading to a change in water cycle within our human civilization system. The determinant coefficients for reduced surface outflow amount and reduced sewer discharge were 0.9164 and 0.9892, respectively, while the determinant coefficient for reduced discharge of sewage treatment plants was 0.9988. This indicates that with an increase in water reuse, surface flow, sewage and discharge from sewage treatment plants all saw a linear reduction.

가속화되는 도시화와 함께 기후변화로 인하여 가중되는 환경 측면의 수질, 생태, 기온, 에너지 이외에도 수문순환에서 발생되고 있는 변화는 우선적으로 해결되어야 하는 중요한 문제임이 확실하다. 이러한 요인은 도시유역 내 불투수면적의 증가에 따라 증발산량의 감소, 지표유출의 증가, 침투량 감소의 물순환 변화를 초래한다. 본 연구에서는 기후변화 및 도시화가 물순환 변동에 미치는 영향을 정량적으로 산정하고 이를 도시지역별로 평가하기 위해 주성분 분석(Principal Component Analysis) 기법을 적용하였다. 낙동강 유역 내 도시화 지역의 발달 정도에 따라 16곳의 동단위의 지역을 선정하였다. 선정된 지역은 면적 대비 도시화율이 10 % 이상인 곳을 기준으로 산정하였으며, 선정된 도시는 대구 동/북구/서구/달성군, 구미, 경산, 구미 및 칠곡, 밀양, 문경 등으로 도시화 정도에 따라 물순환 변동의 대조군을 위한 지역도 함께 선정하였다. 선정된 도시지역 내 물순환 변동 평가 지수에 따라 상관관계 분석을 통하여 주성분 분석의 입력변수를 선정하였다. 주성분 분석을 통하여 정보의 기여율이 98 %를 나타내는 PC3 (Principal Component 3)을 통하여 각 지역별 물순환 특성 변동 지수의 주성분 분석 결과를 선형결합하였다. 이로써 물순환 변동에 따른 종합 민감도 지수를 산출하였으며, 대구 지역이 약 23으로 가장 큰 민감도를 보였고 다음으로 부산, 구미 등으로 나타났다. 본 연구의 결과는 기후변화 및 도시화에 따른 물순환 변동의 결과를 지수로 정량화하여 각 도시별로 산정하였고 이를 주성분분석 기법에 적용함으로써 도시지역별 종합 지표를 산정하였다. 본 연구의 결과는 기후변화 및 불투수면적의 증가가 수문순환에 미치는 영향을 도시별로 가할 수 있으며 물순환 변동 평가기법은 지역을 상세화하여 최대 단위를 동으로 설정하여 적용한다면 도시 개발 및 계획 시 그 활용정도가 높을 것으로 판단된다.

The impacts of climate change and land use change are still causing changes in natural patterns as increase of temperature, rainfall intensity, and frequency of rainfall. Also, urbanization is well known to impact hydrology of basins because of its creation of impervious surfaces. This study has been investigated developing method being able to estimate changes of hydrological properties and assessing these changes on each city. For this study, it used three land use scenarios in 1975, 1990, and 2009 for considering impervious changes and future climate change scenario based on RCP 8.5 for impacts of climate change. Three clusters by k-means clustering method were formed by variables shown high correlations from results of Spearman’s order-rank method and Kendall Tau for various variables as rate of each land cover over area of each subwatershed on 145 subwatersheds in Nakdong River, difference of rate of land cover area and CN (Curve Number) between scenarios based on scenario in 1975, and rate of hydrological properties like rate of evaporation, surface runoff, and groundwater. An assessment method using the results from correlation and cluster analysis was developed for deriving the weighted index in accordance with sensitive degree of hydrological property and increase of impervious area. The assessment method for sensitive city applied principal component analysis (PCA) method. Results show that Daegu is greatly sensitive on impacts of hydrological property and increase of impervious area. Consequently, linear regression equations on Daegu are derived by analysis of hydrologic response unit. Urbanization appeared to increase of surface runoff and decrease of evaporation and groundwater in accordance with change of land uses, also the results are considerably important and useful in case of development and design of city.

Yongsan ward is located at central place connecting south and north ecology axis of seoul. Various environment-friendly Yongsan development could pose positive effects on NPS(non pollutant source) pollutant reductions and water quality improvement at Han-rive because BOD, T-N, and T-P NPS discharges took 90% of total pollutant from this area. In this study, direct runoff and NPS pollutant loads were evaluated before and after development using spatio-tamporal change in CN(curve number) and EMC(event mean concentration) data. It was found that direct runoff value is 23,584,724 m3, and BOD, T-N and T-P loads are 104,456 kg/year, 111,483 kg/year and 7,500 kg/year under pre-development condition, respectively. Annual runoff, BOD, T-N and T-P reducing rate were 12.9%, 33.3%, 35.6% and 40.7% under integrated post-development condition, respectively. Based on the results obtained in this study, environment-friendly urban development could be achieved at Yongsan area.