REMM-based Calculation of Deficit Widths of Rural Riparian Zones and their Remedy Models

Riparian zones play a key role in removal none-point pollution and improving water quality. It is well known that these functions largely depend on the widths of riparian zones. However, due to farm land-use, building construction, road construction and ect. along river corridors in some rural area, some riparian zones have been occupied. It results in that none-point pollution cannot be intercepted efficiently and water quality could be degraded. We have investigated 3 rivers in Baimatang Village of Tongxiang City, Zhejiang Province, China, where is attributed as flat rural area. After we have divided the 3 rivers into 6 reaches (S1, S2,S3,S4,S5,S6) according the land-using patterns and cross-section, the rate of total nitrogen removal of each riparian zone has been calculated with Riparian Ecosystem Management Model(REMM). The results showed that the removal rate in S5 was the biggest, 76%. But in other 5 reaches, the removal rates of nitrogen were less than 75%. In practice, lands outside the riparian zones have been using as farm field or house field along the 5 reaches, the riparian zones was limited and could not been widened. In order to remedy the width deficits, we set 5 experimental blocks with traditional concrete, ecological concrete balls, ecological bags, ecological five-feng bricks and vegetation in reach S1, S2, S3, S4, S6, respectively. Experiments showed that the removal rates of the compound measures of vegetation with ecological concrete balls or ecological bags were improved to 76.07%, 79.81% and their remedied widths were 10.34m and 11.64m, respectively. However, the removal rates of other three measures were still less than 75% and their remedied widths were not obvious. Thus, the compound measures of vegetation with ecological concrete balls or ecological bags have much better nitrogen removal efficiency. Meanwhile, these measures can reduce the width deficits of now widths to satisfy the objectives of buffer the water quality. Additionally, the fitting equations of optimal widths have been presented. It would be helpful to definite the exact width of a riparian zone for river restorations or managements.