Selection and configuration of rainwater harvesting system substituting groundwater irrigation for greenhouse crops in the Bashang region of Hebei Province
The Bashang region of Hebei Province plays the role of ecological barrier and water conservation area for the Jing-Jin-Ji region; however, the main cash crops such as vegetables and potatoes in this region mainly rely on groundwater irrigation, especially the plastic greenhouse crops, which are entirely dependent on groundwater. This has led to excessive consumption of groundwater resources and degradation of the ecological environment. In order to alleviate this problem and respond to the national requirements for the construction of “two zones” and rural revitalization, we proposed an alternative irrigation scheme for greenhouse kidney beans in the Bashang region based on the rainwater harvesting system. The cost effectiveness of different types of rainwater harvesting systems (simple tank, galvanized panel tank, and fiberglass reinforced plastic tank) were examined under different volumes of groundwater supplementary irrigation by water balance principle and Python modelling. The results showed that using the cost of full groundwater irrigation production for 480 m2 of standard greenhouse kidney beans as a reference, the economic size of simple, galvanized panel, and fiberglass tanks filled with rainwater harvested by greenhouse film were 14.4, 9.7, and 4.8 m3, respectively, under the annual precipitation scenario of 80th percentile guarantee rate. The corresponding groundwater substitution rate could achieve 76.4%, 67.5%, and 48.8%, all with inevitable water discharge. The rainwater harvesting and storage irrigation system in the Bashang region of Hebei Province is economically feasible, it can replace a substantial amount of groundwater with rainwater, and alleviate the pressure of regional water resources. Also, the discharged water from the film and other rainwater harvesting surfaces in the greenhouse area can replenish the groundwater, which is conducive to the groundwater health and ecological efficiency.