| Nanhongmen irrigation district is an important water reclamation area inBeijing. Reclaimed water can be used not only in river replenishment, agriculturalirrigation but also in groundwater supplement. Due to the difference of water qualitybetween reclaimed water and surface water, there are growing concerns over theseepage of reclaimed water canal would contaminate groundwater environment. Thisresearch discusses the impact of the reclaimed water canal infiltration towardsgroundwater in Nanhongmen irrigation district and calculates infiltrationreplenishment through field observation towards canal seepage by inflow-outflowmethod and ponding test assisted by GMS software to simulate the distribution ofnitrogen in groundwater. It provides foundation for scientific management andutilization of reclaimed water irrigation. Conclusions of the thesis are as follows:（1） Field experiments in Chahe and Beiyechang Channel show that channeldepth changes in a linear manner with time, and infiltration intensity changes in acurve way with water depth.By calculation, the result shows that the annual infiltration capacity of FengheRiver is around2.96million cubic meter and that of Chahe River1.04million cubicmeter. And the total infiltration capacity of the irrigation district is around4millioncubic meter, showing3.6%error ratio with the numerical simulation of infiltrationreplenishment of reclaimed water which is4.15million cubic meter.（2） The result of numerical stimulation indicates that reclaimed watersupplements the groundwater by13.15million cubic meter annually through whichreclaimed water channel takes up31.6%and reclaimed water irrigation68.4%.Therefore, infiltration from irrigation serves as the major way of reclaimed watersupplementing groundwater. Statistics of groundwater level monitoring proves thatgroundwater level depression rate in reclaimed water irrigation district is much lowerthan that of in non-reclaimed water irrigation areas. In conclusion, the utilization ofreclaimed water to some extent relieves the water resource tension in this region.（3） The result of solute transport stimulation shows that NH4-N and NO3-N intensity in groundwater of surrounding areas increases on year-on-year basis.However only a very limited areas alongside the banks are affected. By2030ammonia nitrogen in groundwater nearby Chahe River and Fenghe River will exceedthe limits, and the maximum migration distances of it around Fenghe River andChahe River under the present condition are186.5meters and120metersrespectively. The intensity of nitrate nitrogen in groundwater of the two rivers ismaintained under a safe level with its maximum migration distances200meters and138meters.（4） The overall input of nitrate nitrogen in groundwater of the researched area is3353.26t/a of which40.59t/a is from channel leakage, accounting for1.21%of thetotal volume. And the overall input of ammonia nitrogen in groundwater of theresearched area is1627.38t/a of which27.74t/a is from channel leakage, taking up1.69%of the total volume. In conclusion, channel leakage is not the main source ofnitrogen in groundwater in researched areas. |
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