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1 南阳洼涝地的成因1.1 地形低洼。南阳盆地西、北、东三面环山,南部缺口微向南倾斜,中间低平,全区大部为近代冲积物覆盖,有少数孤山残岗,是河南省最大的山间外流盆地,又称南阳坳陷。砂姜黑土分布在南阳盆地中南部平缓平原区,该区地面平缓开阔、气候温和、雨量充沛、水源丰富,特别是盆地里唐白河流域的中下游地区,地势低平,坡降小(有的达万分之一),地下水位高,通常在1～2m之间,雨季来临时地下水位马上升到1m或接近地表,一些湖洼地常有季节性积水。由此说明,地形低洼是南阳市砂
1 causes of Nanyang waterlogged land 1.1 low-lying terrain. The Nanyang basin is surrounded by mountains on three sides in the west, north and east. The southern gap is slightly inclined to the south and low in the middle. Most of the area is covered by modern alluvial deposits. There are a few gushan residues, which are the largest mountain outflow basins in Henan Province. Nanyang depression. Shajiang black soil is distributed in the plain plains area of south-central part of Nanyang basin. The surface of the area is flat and open with mild climate, abundant rainfall and abundant water resources. Especially in the middle and lower reaches of the basin, The water table is high, usually between 1 ~ 2m. When the rainy season arrives, the groundwater level rises to 1m or close to the surface, and some lakes often have seasonal waterlogging. This shows that the low-lying terrain is Nanyang sand