Analysis on investment and benefit of harvested rainwater utilization in the northwest loess Plateau

The paper is based on an experimental study on in-situ rainwater harvesting by irrigating several selected crops,spring wheat,watermelon,broccoli and cucumber.The experiments were conducted at the Gaolan Station of Agricultural and Ecological Experiment (Gaolan County,Gansu Province),Chinese Academy of Science,in 2000-2001,in order to explore the rate of rainfall-runoff,compare the micro-catchment's cost of various types of water collection,analyze the storage cost of various water cellars,and investigate the unit yields and water use efficiency (WUE),production values of the selected crops and the production value per cubic water.The results indicated that,the costs of both micro-catchments and storage of harvested rainwater are averagely expensive,which accounted for.1.07-RMB.m^-3 and 5.08-RMB.m^-3,respectively,with a higher water storage cost.The cucumber in solar greenhouse has the highest values in both net production and production per cubic water,followed by broccoli in open field,watermelon in gravel-mulched field,and wheat in open field for the comparable values.All the net production values of wheat are negative if the investment of manual work is considered; supplementary irrigation causes the decrease of the net production values to a great degree.In contrast,harvested rainwater for micro-irrigation of watermelon in gravel-mulched field,of broccoli and cucumber in solar greenhouse brought large benefit.We may get a conclusion that the model of “one cellar and one pond” for solar greenhouse is the effective catchments-storage-high utilization of rainwater model for solar greenhouse in the region with an annual precipitation of 300 mm.