Analysis On The Variation Characteristics Of The Constructed Wetlands--Ponds In The Changwu County

Ponds provide a very important landscape for the Loess Plateau. However, with the rapid development of economy and society and the full swing of the new rural construction, these constructed wetlands are slowly disappearing. To study the evolution processes, variation characteristics, influence factors and possible functions in supplying to the groundwater of the ponds, which provides not only a scientific basis for ponds’ sustainable development but also an important reference significance for people’s expectation to rebuild ponds. Based on four sites’ survey data for the ponds in Changwu County, this article made some analyses on the dynamic variational characteristic of the ponds, the evolving situation of ponds, the possible functions in supplying to the groundwater and effecting factors of ponds’ changing. It as well refers how to protect and recover the ponds in future. The main research results are:(1) The number and area of ponds generally show a decreasing trend in the study period. In the early 1980 s, the changes were relatively flat. However, the shrinking rate got faster in the later years. From the year 2010 to 2014, the number and area of ponds reduced at the maximum rate of-5.71% and-4.80%, respectively. It is different from the sharp reduction in the total area and number of ponds that the average area of the ponds in Changwu County are increasing constantly in different periods. The average area is 253 m2 in the early 1960 s,288 m2 in the early 1990 s, until up to 325 m2 in 2014. These changing data show: In 55 years, although the number of small ponds have reduced much as well as big ponds, the big ponds have been reserved. By 2014, there are only five ponds(10 km2) alive. The number of disappearing ponds is 75.0% of total ponds. The existing ponds’ area is 171 m2/km2. There are two ways to store water--seasonal storage and temporary storage. And the ponds’ number of seasonal storage is 80.0% of the total existing ponds. It mainly stores water in July, August and September.(2) The groundwater declines seriously in research area. The supplying to groundwater mainly comes from the rainfall infiltration. In a certain extent, ponds can supply to groundwater by collecting rainwater from yards. As the ponds area reducing, the groundwater level declined correspondingly, which can also be expressed that the decreasing of ponds’ replenishment may cause changes in the groundwater level.(3) Human activities directly affect on ponds, which determines the evolution and change directions. The population of Changwu County rapidly grows from 1964 to 2011, which irritate the increase of people’s demands. And the land for living and transportation is increasing. So it leads the ponds are occupied by residents. Meanwhile, with the economic and social rapid development, people’s production and living conditions greatly improved. And in-depth of the new rural construction, rural production and living ways have taken place greatly, which restrict the survival of the ponds further. The interference of human activities not only influence the number of ponds but also the quality. There are there main aspects to influence on their change. They are the way of using water for human and domestic animal, people’s management and policies.(4) In the 21 st century, in order to realize the harmony of man and nature, the sustainable development of man and society and the construction of ecological civilization, people must adjust measures to local conditions to develop water conservancy project. To restore a certain size ponds are need the people’s attention. Ponds in the process of reconstruction, recovery and reconstruction not only consider the benefits to the flood control, the ponds should be construction for water storage, drainage, the leisure, the view of an integrated construction project,so people are supposed to pay more attention to them, which requires to strengthen the related technology research, pay attention to the participation, promote the sustainable development of the ponds, at the same time, the village should play the dominant role in the restoration and reconstruction of ponds. Ponds should be play a active role in sustainable development of rural ecological-social-economy.