Groundwater recharge from irrigated cropland in the North China Plain: case study of Luancheng County, Hebei Province, 1949–2000

Abstract

Abstract:Effective management of limited water resources in the North China Plain requires reliable calculation of historical groundwater balances at local, sub-watershed scales. These calculations typically are hindered by poorly constrained recharge estimates. Using a simple soil-water balance model, we independently calculated annual recharge from irrigated cropland to unconfined alluvial aquifers underlying Luancheng County, Hebei Province, in the western part of the North China Plain, for 1949-2000. Model inputs include basic soil characteristics and daily precipitation, potential evapotranspiration, irrigation, crop root depth, and leaf-area index; model outputs include daily actual evapotranspiration and areal groundwater recharge. Results indicate that areal recharge is not a constant fraction of precipitation plus irrigation, as previously assumed, but rather the fraction increases as the water inputs increase. Thus, model-calculated recharge rates range from 5 to 109 cm year 1 , depending on the quantity of precipitation and irrigation applied. The important implication is that, because this drainage recharges the underlying aquifer, improving irrigation efficiency by reducing seepage does not save water. This explains why successful efforts to reduce groundwater pumping for irrigation have had no effect on water-table declines. So long as crop cover is extensive and all crop-water requirements are met-which has been the case in Luancheng County since the 1960s-groundwater levels will continue to decline at a steady rate. Potential solutions include reducing the irrigated area, reintroducing fallow periods, and shifting water from agriculture to other, less consumptive uses.

Evaluation of optimal irrigation scheduling and groundwater recharge at representative sites in the North China Plain with SWAP model and field experiments

“…For example, assuming that the specific yield of the aquifer was 0.2 and all the irrigation came from groundwater, potential decline in water table under the optimal irrigation scheduling was about 1.30 m yr À1 in LC. This result roughly matched the calculated groundwater level decline of about 1-1.5 m yr À1 in LC by the other studies (Chen et al, 2010;Kendy et al, 2004;Zhang et al, 2003).…”

“…The more precipitation usually resulted in greater groundwater recharge in each representative Table 7 Water balance components for winter wheat and summer maize under optimal and reference irrigation scheduling (abbreviated as ''O'' and ''T'') site. According to the reports of Kendy et al (2004), the fraction of recharge accounting for precipitation plus irrigation increased with water input. Furthermore, the relationship between precipitation and groundwater recharge was also affected by the variation of water table depth, especially in shallow water table area.…”

“…In the NCP, Kendy et al (2004) showed that areal recharge in Luancheng was not a constant fraction of the plus of precipitation and irrigation, but rather the fraction increased with the increase of water inputs. Chen et al (2010) estimated the response of recharge to historical climate and irrigation, and they explored the optimal water management strategies in Luancheng using the APSIM model.…”

Towards groundwater neutral cropping systems in the Alluvial Fans of the North China Plain

“…But often this also leads to reduced drainage (D) so that the net effect is that groundwater levels keep going down (Kendy, 2003;Kendy et al, 2003Kendy et al, , 2004. Hence, irrigation needs to be reduced by a greater amount than the current net extraction from ground water.…”

“…However, if at unchanged irrigation input the drainage is reduced, then increased water use efficiencies will actually speed up groundwater decline. Increasing efficiency is therefore not a sufficient solution to the problem of declining water resources (Kendy 2003;Kendy et al, 2003Kendy et al, , 2004.…”