Climatic controls on diffuse groundwater recharge across Australia

Abstract

Reviews of field studies of groundwater recharge have attempted to investigate how climate characteristics control recharge, but due to a lack of data have not been able to draw any strong conclusions beyond that rainfall is the major determinant. This study has used numerical modeling for a range of Köppen-Geiger climate types (tropical, arid and temperate) to investigate the effect of climate variables on recharge for different soil and vegetation types. For the majority of climate types the total annual rainfall had a weaker correlation with recharge than the rainfall parameters reflecting rainfall intensity. In regions with winter-dominated rainfall, annual recharge under the same annual rainfall, soils and vegetation conditions is greater than in regions with summer-dominated rainfall. The relative importance of climate parameters other than rainfall is higher for recharge under annual vegetation, but overall is highest in the tropical climate type. Solar radiation and vapour pressure deficit show a greater relative importance than mean annual daily mean temperature. Climate parameters have lowest relative importance in the arid climate type (with cold winters) and the temperate climate type. For 75% of all considered cases of soil, vegetation and climate types recharge elasticity varies between 2 and 4, indicating a 20% to 40% change in recharge for a 10% change in annual rainfall Understanding how climate controls recharge under the observed historical climate allows more informed choices of analogue sites if they are to be used for climate change impact assessments

Changes in Köppen-Geiger climate types under a future climate for Australia: hydrological implications

“…Barron et al (2012) showed that groundwater recharge under BSh is higher for a given annual rainfall than Cfa but BSh by definition experiences a lower rainfall than Cfa (Peel et al, 2007). The majority of the areas projected to transition from temperate (C) to arid (B) under a future climate are also projected to have a reduction in recharge , the analysis of Barron et al (2012) suggests that the reduction in recharge would have been greater without the change in climate type. For a future climate of +2.4 • C, 24 % of the country is projected to change climate type.…”

Precipitation Intensity Effects on Groundwater Recharge in the Southwestern United States

“…Results summarized in Table 2 suggest slight changes in precipitation intensity with magnification factors generally less than 1 for return periods of 2, 5 and 10 years. Such changes in precipitation intensity have been shown to dramatically alter recharge [25,27,74]. Magnification factors for several sites, Site E for example, exhibit reduced magnitudes for short-duration events and increased magnitude for longer-duration events.…”

“…Also, soil moisture likely decreases to levels below the wilting point as a result of high PET between rare episodic precipitation events. Thus, we anticipate that small changes in precipitation intensity, which can have a considerable impact on recharge [27] may result in a change in the R:P ratio. It is important to recognize that changes in groundwater storage, as evaluated in the MRC (Section 3.1) is not a factor in shifts in the R:P ratio as changes in dh/dt have been accounted for prior to the estimation of recharge from the groundwater hydrograph.…”

“…This significant change in slope suggests an imbalance in the physical recharge behaviors in the system. To evaluate the potential imbalance, we ponder the climatic factors which could alter the ratio of R:P, including antecedent soil moisture conditions, changes in soil moisture storage, changes in evapotranspiration (ET) rates or changes in precipitation intensity [27]. As the region is arid, it is unlikely that antecedent soil moisture conditions would vary greatly between episodic recharge events.…”

“…Groundwater recharge varies spatially as a result of physical attributes including soil type, depth to groundwater, vadose zone porosity, hydrogeology and precipitation patterns. Because of the episodic nature of recharge in arid environments, small changes in precipitation intensity have been suggested to influence groundwater recharge [26,27]. Recent studies have sought to quantify episodic recharge [28] or identify regional groundwater recharge [10,11,23].…”