Evapotranspiration partitioning using an optimality-based ecohydrological model in a semiarid shrubland

Partitioning of evapotranspiration(ET)into biological component transpiration(T)and non-biological component evaporation(E)is crucial in understanding the impact of environmental change on ecosystems and water resources.However,direct measurement of transpiration is still challenging.In this paper,an optimality-based ecohydrological model named Vegetation Optimality Model(VOM)is applied for ET partitioning.The results show that VOM model can reasonably simulate ET and ET components in a semiarid shrubland.Overall,the ratio of transpiration to evapotranspiration is 49%for the whole period.Evaporation and plant transpiration mainly occur in monsoon following the precipitation events.Evaporation responds immediately to precipitation events,while transpiration shows a lagged response of several days to those events.Different years demonstrate different patterns of T/ET ratio dynamic in monsoon.Some of the years show a low T/ET ratio at the beginning of monsoon and slowly increased T/ET ratio.Other years show a high level of T/ET ratio for the whole monsoon.We find out that spring precipitation,especially the size of the precipitation,has a significant influence on the T/ET ratio in monsoon.

Water yield and biomass production for on a eucalypt-dominated Mediterranean catchment under different climate scenarios

Worldwide,forests are vital in the regulation of the water cycle regulation and in water balance allocation.Knowledge of ecohydrological responses of production forests is essential to support management strategies,especially where water is already scarce.Shifting climatological patterns are expected to impact thermopluviometric regimes,water cycle components,hydrological responses,and plant physiology,evapotranspiration rates,crop productivity and land management operations.This work(1)assessed the impacts of different predicted climate conditions on water yield;(2)inferred the impacts of climate change on biomass production on eucalypt-to-eucalypt succes sion.To this end,the widely accepted Soil and Water Assessment Tool(SWAT)was run with the RCA,HIRHAM5 and RACMO climate models for two emission scenarios(RCP 4.5 and8.5).Three 12-year periods were considered to simulate tree growth under coppice regime.The results revealed an overall reduction in streamflow and water yield in the catchment in line with the projected reduction in total annual precipitation.Moreover,HIRHAM5 and RACMO models forecast a slight shift in seasonal streamflow of up to 2 months(for2024-2048)in line with the projected increase in precipitation from May to September.For biomass production,the extreme climate model(RCA)and severe emis sion scenario(RCP 8.5)predicted a decrease up to 46%.However,in the less extreme and more-correlated(with actual catchment climate conditions)climate models(RACMO and HIRHAM5)and in the less extreme emission scenario(RCP 4.5),biomass production increased(up to 20%),and the growth cycle was slightly reduced.SWAT was proven to be a valuable tool to assess climate change impacts on a eucalypt-dominated catchment and is a suitable decision-support tool for forest managers.