TY - JOUR

T1 - Coupling saturated and unsaturated flow

T2 - Comparing the iterative and the non-iterative approach

AU - Brandhorst, Natascha

AU - Erdal, Daniel

AU - Neuweiler, Insa

N1 - Funding Information: Deutsche Forschungsgemeinschaft in the framework of research unit FOR 2131 (grant no. NE 824/12-1) and the Collaborative Research Center CAMPOS (CC 1253 CAMPOS – Catchments as Reactors) (grant no. CRC 1253). Funding Information: Financial support. This research has been supported by the

PY - 2021/7/9

Y1 - 2021/7/9

N2 - Fully integrated three-dimensional (3D) physically based hydrologic models usually require many computational resources. For many applications, simplified models can be a cost-effective alternative. The 3D models of subsurface flow are often simplified by coupling a 2D groundwater model with multiple 1D models for the unsaturated zone. The crucial part of such models is the coupling between the two model compartments. In this work we compare two approaches for the coupling. One is iterative where the 1D unsaturated zone models go down to the impervious bottom of the aquifer, and the other one is non-iterative and uses a moving lower boundary for the unsaturated zone. In this context we also propose a new way of treating the specific yield, which plays a crucial role in linking the unsaturated and the groundwater model. Both models are applied to three test cases with increasing complexity and analyzed in terms of accuracy and speed compared to fully integrated model runs. The non-iterative approach is faster but does not yield a good accuracy for the model parameters in all applied test cases, whereas the iterative one gives good results in all cases. Which strategy is applied depends on the requirements: computational speed vs. model accuracy.

AB - Fully integrated three-dimensional (3D) physically based hydrologic models usually require many computational resources. For many applications, simplified models can be a cost-effective alternative. The 3D models of subsurface flow are often simplified by coupling a 2D groundwater model with multiple 1D models for the unsaturated zone. The crucial part of such models is the coupling between the two model compartments. In this work we compare two approaches for the coupling. One is iterative where the 1D unsaturated zone models go down to the impervious bottom of the aquifer, and the other one is non-iterative and uses a moving lower boundary for the unsaturated zone. In this context we also propose a new way of treating the specific yield, which plays a crucial role in linking the unsaturated and the groundwater model. Both models are applied to three test cases with increasing complexity and analyzed in terms of accuracy and speed compared to fully integrated model runs. The non-iterative approach is faster but does not yield a good accuracy for the model parameters in all applied test cases, whereas the iterative one gives good results in all cases. Which strategy is applied depends on the requirements: computational speed vs. model accuracy.

UR - http://www.scopus.com/inward/record.url?scp=85109714634&partnerID=8YFLogxK

U2 - 10.5194/hess-25-4041-2021

DO - 10.5194/hess-25-4041-2021

M3 - Article

AN - SCOPUS:85109714634

VL - 25

SP - 4041

EP - 4059

JO - Hydrology and Earth System Sciences

JF - Hydrology and Earth System Sciences

SN - 1027-5606

IS - 7

ER -