| Danjiangkou Reservoir is the national water source region of drinking water, and it is also water source region of the South-North Water Transfer Project. Its water quality security is related to the whole river basin and the region which received the water by the transfer project. In recent years, Danjiangkou Reservoir, especially its tributaries and the river mouth, receives tremendous pollution input because of effect of urbanization, intensification of social water, weakness of natural water by contraries. Nutritive salt, heavy metals and other organic pollutants brings a tremendous threat to its water quality security. This paper mainly cared about Danjiangkou Reservoir water quality eutrophication and safety problems. Based on classification of main tributaries, through choosing the typical tributary, the mechanism, the accumulation and the form variation rule of pollutants were analyzed on the basis of reservoir operation and fluctuation law of influence on seasonal rainfalls. The loss of nonpoint source from Agriculture and the transport processes in the wet-dry zone of TSS、N and P pollution source were researched to study the capability of riparian zone, which subside, transform and resort pollutants. The main achievements are exhibited as below:(1) Danjiangkou Tributaries fuzzy classification results show that the all of the tributarie’s situation is well, rivers healthy level distribution on1to4, Du river, Danjiang river belongs to the the first level; Qi River, Tao River,Laoguan river belongs to the second level; Tian river, Guanshan river belongs to the thrid level; Shending river, Jiang River, Si river, Lang river belongs to the forth level. About pollution characteristics, the heavy metal pollution is more serious in Lang river; Jian river, Shending river, Jiang river got a seriously polluted about organic consumed oxygen; Tributaries overall nutrient pollution is more prominent.(2) Terraced farming is helpful to water and soil conservation, reduce phosphorus loss; slope and soil nitrogen loss shows positively correlated; artificial plowing farming activities, can effectively reduce surface runoff. The output of phosphorus runoff with greater morphological differences, dissolved phosphorus migration dominated mostly by SRP, while the output of dissolved nitrogen are more than84%.(3)6m width riparian has better resistance control role in the output surface of TP, while on the riparian with a length greater than8m, TN concentration gradually decreases as the length increases. The effect of TP retention is best with low flow, high flow take second place; NH4-N retention efficiency is very stableshore with large flow in riparian. The filtration effect on TSS with runoff in the bermudagrass riparian is not obvious.(4) The process about phosphorus in the soil and water interface is stripping-adsorption-Dissolution-re-adsorption. Soil phosphorus releases to water forms-based on Fe/Al-P, Content of reactive phosphorus (BAP) in TP are in the order: beach (41%)> Heath (32%)> grassland (27%)> orchard (16%)> Farmland (9%), the main risk of phosphorus loss from the beach. In study area the content of transformative Nitrogen Nitrogen (TF-N) is generally low, accounting for TN percentages ranging from20%to36%, indicating that the risk of nitrogen release in the drawdown area after flooded is less. |
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