Including the dynamic relationship between climatic variables and leaf area index in a hydrological model to improve streamflow prediction under a changing climate

摘要

Anthropogenic climate change is projected to enrich the atmosphere withcarbon dioxide, change vegetation dynamics and influence the availability ofwater at the catchment scale. This study combines anonlinear model for estimatingchanges in leaf area index (LAI) due to climatic fluctuations with thevariable infiltration capacity (VIC) hydrological model to improve catchmentstreamflow prediction under a changing climate. The combined model wasapplied to 13 gauged sub-catchmentswith different land cover types (crop, pasture and tree) in theGoulburn–Broken catchment, Australia, for the "Millennium Drought"(1997–2009) relative to the period 1983–1995, and for two future periods(2021–2050 and 2071–2100) and two emission scenarios (RepresentativeConcentration Pathway (RCP) 4.5 and RCP8.5) which were compared with thebaseline historical period of 1981–2010. This region was projected to bewarmer and mostly drier in the future as predicted by 38 Coupled ModelIntercomparison Project Phase 5 (CMIP5) runs from 15 global climate models(GCMs) and for two emission scenarios. The results showed that during theMillennium Drought there was about a 29.7–66.3 % reduction in meanannual runoff due to reduced precipitation and increased temperature. Whendrought-induced changes in LAI were included, smaller reductions in meanannual runoff of between 29.3 and 61.4 % were predicted. The proportionalincrease in runoff due to modeling LAI was 1.3–10.2 % relative to notincluding LAI. For projected climate change under the RCP4.5 emissionscenario, ignoring the LAI response to changing climate could lead to afurther reduction in mean annual runoff of between 2.3 and 27.7 % in thenear-term (2021–2050) and 2.3 to 23.1 % later in the century(2071–2100) relative to modeling the dynamic response of LAI toprecipitation and temperature changes. Similar results (near-term2.5–25.9 % and end of century 2.6–24.2 %) were found for climatechange under the RCP8.5 emission scenario. Incorporating climate-inducedchanges in LAI in the VIC model reduced the projected declines in streamflowand confirms the importance of including the effects of changes in LAI infuture projections of streamflow.