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发表于 2014-8-19 08:07
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本帖最后由 给快乐加加油 于 2014-8-19 09:12 编辑 $ v+ ~1 K# f; Z) {6 M
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What is the difference between a wetland and a pond？
$ k$ K9 X }8 e' d s3 OAS: Most wetlands are naturally occurring and can be identified by the presence of plants such as cattails that are adapted to wet areas, and by the appearance of water that is either on or just below the surface for at least part of the year. In addition, wetlands soils usually differ in color and content from the surrounding upland soils. A pond may refer to any small body of water, including a drainage pond, wetland, or even a natural depression that floods during a rainstorm。
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MM: What’s the purpose of a drainage pond?
& {- w3 r, R- Z$ cAS: Drainage, or storm water, ponds are man-made and are designed to collect storm water from streets, roofs, parking lots and other surfaces. Drainage ponds protect wetlands by pre-treating storm water and reduce flooding and erosion by capturing heavy rainfall and releasing it slowly into adjacent waterways. They also allow some of the sediment and nutrients in the water to settle out before being released into the nearest wetland, lake, or creek. Because drainage ponds usually hold water for at least part of the year, over time they may develop the appearance of a wetland.# B# _- w& w- l$ Q! F; B. q
! J0 W! ~! @' N; G$ O; `3 K1 DAS: Not necessarily. Culverts, outlet pipes, or other drainage structures may be present in either a drainage pond or a wetland. In addition, wetlands may have been partially excavated in the past in order to retain additional storm water or altered as the result of development and may appear similar to a drainage pond.
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: So, a pond may be a wetland, and a wetland might be a drainage pond or a pond, and a drainage pond might look like a pond or a wetland. How is a resident supposed to know for sure what type of water resource they have on their property?& f5 ?! `; q) o4 G+ A3 I8 n
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楼主: 给快乐加加油
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发表于 2014-8-13 21:10
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不属于校区，看着孩子很多，本区的都人满为患了。杞人总爱忧天。
