Vulnerability of shallow ground water and drinking-water wells to nitrate in the United States: Model of predicted nitrate concentration in shallow, recently recharged ground water -- Input data set for drainage ditch (gwava-s_ddit)

This data set represents the area of National Resources Inventory surface drainage, field ditch conservation practice, in square kilometers, in the conterminous...本数据集以平方千米为计量单位，记录了美国本土毗邻区域（conterminous）内国家资源清查（National Resources Inventory）项下的地表排水与田间沟渠保护措施的覆盖面积……