| Waterways play an important recreational and ecological role in modern citieswhere citizens live in harmony with urban environment. Compared with natural rivers,waterways in cities have a slower flow, a reduced self-purification capability, anincreased risk of eutrophication and a raised cost for maintenance. Maintaining waterquality and quantity in urban waterways proves to be a comprehensive issueconcerning water resources, aquatic environment, urban ecology and socio economy.The paper is a case study of the new drainage-aquatic system in Songbei Districtof Harbin (including Fasheng canal and its south branch canals). The waterways relyon gates and pumps to draw and drain water and guarantee water safety due to thecharacter of the low-lying outer-river to inner-river in the area. The paper evaluatestwo types of operational schemes for ensuring water safety and achieving maximumsocial and economic benefits at minimum financial cost.The origin of contaminants into waterways is indentified and the contaminants’characteristics are then analyzed. Contaminant sources include the channel flow fromthe Songhua River in Harbin and the local stormwater runoff. Three pollutionindicators (COD, BOD5, NH3-N) are used to estimate the annual total contaminantsand to forecast the changing water quality in the canals.Evaluation of water quality in the canals is then conducted by using the averageestimation method. Three pollution indicators’ contributions to the deterioration ofwater quality are singled out, based on which the timing of water diversion anddrainage is determined to meet the IV-standard of water quality.The period from June to September is prone to water eutrophication and flood.To ensure water quality, two water channeling and draining schemes are compared interms of costs. The ELCIRC model is used to simulate flow and water quality in thewaterways. Lastly with consideration of social and economic benefits, the optimizingwater channeling and draining scheme is proposed. |
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