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A linked surface water-groundwater modelling approach to more realistically simulate rainfall-runoff non-stationarity in semi-arid regions

Author:
Deb, Proloy, Kiem, Anthony S., Willgoose, Garry
Source:
Journal of hydrology 2019
ISSN:
0022-1694
Subject:
climatic factors, drought, groundwater, hydrologic models, runoff, semiarid zones, surface water, watersheds, Australia
Abstract:
Interactions between surface water (SW) and groundwater (GW) have been identified as a major contributing factor to non–stationarity in rainfall–runoff relationships. However, because existing rainfall–runoff models do not realistically account for these SW-GW interactions, they fail to robustly simulate runoff during multi-year droughts, especially in arid and semi-arid catchments that are relatively flat. Therefore, this study introduces a linked SW-GW modelling approach and tests it under different climatic conditions (Average, Dry and Wet periods) in two heterogeneous, semi-arid catchments in southeast Australia (SEA). The linked SW-GW modelling approach includes a fully-distributed SW (i.e. rainfall-runoff) model (SWATgrid) and a three-dimensional finite–difference GW model (MODFLOW). The results show that the linked SW-GW modelling approach produces highly improved runoff simulations for the study catchments, especially during dry conditions. These findings demonstrate the importance of accounting for SW-GW interactions when conducting rainfall-runoff modelling and highlights that failing to do so will result in overestimation of runoff during droughts – this is salient given projections for hotter and drier futures in many semi-arid regions. Although the study is focused on SEA, the insights gained are highly applicable for water managers in any region that experience high hydroclimatic variability or change.
Agid:
6440929