Comparison of JULES and a distributed recharge model

The modified EA−FA0 method in ZOODRM (Griffiths et al. 2006) produces similar evapotranspiration to JULES, although in dry years it predicts lower evapotranspiration. The soil column in JULES provides storage, which delays and smooths the recharge signal. ZOODRM predicts significantly more recharge and less surface runoff than JULES. ZOODRM matches the surface runoff determined by baseflow separation (Gustard et al. 1992) more closely than JULES, which is expected because the runoff coefficients in ZOODRM were calibrated based on baseflow separation. It is interesting that during the winter of 2000-2001, when groundwater flooding occurred in the Chalk aquifer, JULES matches the observed surface runoff more closely than ZOODRM.