新加坡都市降雨逕流及水質分析

Analyses of Urban Storm Water Quantity and Quality in Singapore

陳美清(Bee Ching Tan)

指導教授 ： 徐年盛

國立臺灣大學/工學院/土木工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.10527

摘要

近年來新加坡因為經濟、工業的迅速發展以及生活品質提升，促使遊憩、觀光業蓬勃發展，在高度開發下，集水區內不透水面積逐漸增加，使得地表的透水率及水源涵養能力降低，造成地表逕流與暴雨洪峰流量增加，因此地表的污染物質大量被沖刷至河川水體，造成水質惡化。
本研究之目的在建立一套方法來評估集水區長期流量及污染負荷量。研究過程中，先收集相關流量及水質資料以供模擬之用。在流量方面，應用美國環保署(U.S.EPA)所研發之暴雨分析模式XP-SWMM，推估克蘭芝(Kranji)集水區暴雨逕流量，並利用經驗公式推估基流量，相加得到總流量，再利用總流量分別估算雨天和晴天的流量。另一方面，本研究利用事件濃度平均法(event mean concentration，EMC)及建立暴雨時期污染物與流量之關係式(rating curve)模擬雨天(wet weather)之負荷量；晴天(dry weather) 負荷量則是利用平均濃度法來推估，最後在評估不同土地使用下，對污染負荷量之影響，研究結果顯示，超過87%之總懸浮固體(TSS)於暴雨逕流帶到承受水體；此外，子集水區CP1、CP2、CP6和CP7測站大部份污染物都是經由暴雨逕流進入承受水體，而子集水區CP4( 23%墓地與8%之軍用地)之污染主要來自晴天污染量，除了總磷(TP)、磷酸鹽(OP)、溶解性有機磷(DOP)、總溶解磷磷酸鹽(TDP)和總懸浮固體(TSS)以外。
本研究提出之分析方法可提供未設測站之鄰近集水區評估水質與地表逕流之情況；在暴雨時期之水質模擬結果亦可提供下游水庫或原水處理廠決策之重要參考依據。

關鍵字

暴雨逕流 ； 土地利用 ； 事件濃度平均法 ； 污染物負荷量

並列摘要

Urbanization has occurred in Singapore over the recent decades concurrent with the growth of Singapore’s population and economy. The process of urbanization has significantly impacted both the storm runoff volume and the timing and magnitude of the peak runoff rate. Urbanization also increases the variety and amount of pollutants transported to receiving waters, causing surface water quality deterioration. Studies on stormwater quantity and quality are hence vital for planning and managing water resources for catchments subjected to human perturbations. The objective of this study is to develop an approach for estimating long term runoffs and pollutant loadings for the Kranji catchment in Singapore, particularly as functions of land use.
The study first established the rainfall-total runoff relationships and total runoff-pollutant loading rate relationships in Kranji Catchment, Singapore. Storm water data were measured and used for calibration and verification of the XP-SWMM model. The calibrated XP-SWMM model was then applied for continuous simulation of catchment runoffs over the 2005-2007 period. The results from XP-SWMM simulations showed that the model is capable of providing good results for continuous flow simulations, and is highly efficient for the estimation of urban storm water direct runoff volumes.
The relationship between rainfall and runoff for the gauged period at each study site shows good correlations. The runoff coefficient (total flow/rainfall ratio) is found to be a function of the total rainfall and land use. In comparing gauging stations CP2 with CP4, the average runoff coefficient is about 3 times higher for CP2, which has the largest proportional area which is developed, around 68%, comprising mainly residential land use with high impervious land cover. In contrast, CP4, which has the largest proportional previous areas, has the lowest runoff coefficient of 0.13.
This study covered thirteen water quality parameters which are considered relevant for water quality management: ammonium-equivalent nitrogen (NH3-N), dissolved organic carbon (DOC), particulate organic carbon (POC), total nitrogen (TN), total dissolved nitrogen (TDN), nitrate+nitrite (NOx), dissolved organic nitrogen (DON), total phosphate (TP), total dissolved phosphate (TDP), ortho-phosphate (OP), dissolved organic phosphorus (DOP), silica (SiO2), and total suspended solids (TSS). A good knowledge of the relative pollutant load contributions from dry-weather flow (DWF) and wet-weather flow (WWF) could provide useful guides for implementing effective and efficient water quality management measures for the sub-catchments. This study uses a regression approach to estimates the WWF loads, and uses the monitored data to estimate the DWF loads. The annual DWF and WWF pollutant loadings were characterized over the 2005-2007 period. For nearly all the pollutants studied, contributions from WWF are greater than DWF at CP1, CP2, CP6 and CP7. However, almost all quality parameters show larger contributions from DWF than WWF at CP4, except for TP, TDP, DOP, OP and TSS. The results suggest that DWF quality control measures may be important for CP4. On the other hand, WWF quality management may be important for CP1, CP2, CP6 and CP7.
The analytical approach developed in this study can be applied to other ungauged watersheds near the study site. The results of this study will provide a better understanding on both the flow and nutrient loading into the reservoir which will aid the overall management objective of nutrient load reduction.

並列關鍵字

Stormwater ； land use ； event mean concentration ； pollution loading rate

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