Comparing SWAT with SWAT-MODFLOW hydrological simulations when assessing the impacts of groundwater abstractions for irrigation and drinking water

Abstract

Abstract. Being able to account for temporal patterns of streamflow, the distribution of groundwater resources, as well as the interactions between surface water and groundwater is imperative for informed water resources management. We hypothesize that, when assessing the impacts of water abstractions on streamflow patterns, the benefits of applying a coupled catchment model relative to a lumped semi-distributed catchment model outweigh the costs of additional data requirement and computational resources. We applied the widely used semi-distributed SWAT model and the recently developed SWAT-MODFLOW model, which allows full distribution of the groundwater domain, to a Danish, lowland, groundwater-dominated catchment, the Uggerby River Catchment. We compared the performance of the two models based on the observed streamflow and assessed the simulated streamflow signals of each model when running four groundwater abstraction scenarios with real wells and abstraction rates. The SWAT-MODFLOW model complex was further developed to enable the application of the Drain Package of MODFLOW and to allow auto-irrigation on agricultural fields and pastures. Both models were calibrated and validated, and an approach based on PEST was developed and utilized to enable simultaneous calibration of SWAT and MODFLOW parameters. Both models demonstrated generally good performance for the temporal pattern of streamflow, albeit SWAT-MODFLOW performed somewhat better. In addition, SWAT-MODFLOW generates spatially explicit groundwater-related outputs, such as spatial-temporal patterns of water table elevation. In the abstraction scenarios analysis, both models indicated that abstraction for drinking water caused some degree of streamflow depletion, while abstraction for auto-irrigation led to a slight total flow increase (but a decrease of soil or aquifer water storages, which may influence the hydrology outside the catchment). In general, the simulated signals of SWAT-MODFLOW appeared more plausible than those of SWAT, and the SWAT-MODFLOW decrease in streamflow was much closer to the actual volume abstracted. The impact of drinking water abstraction on streamflow depletion simulated by SWAT was unrealistically low, and the streamflow increase caused by irrigation abstraction was exaggerated compared with SWAT-MODFLOW. We conclude that the further developed SWAT-MODFLOW model calibrated by PEST had a better hydrological simulation performance, wider possibilities for groundwater analysis, and much more realistic signals relative to the semi-distributed SWAT model when assessing the impacts of groundwater abstractions for either irrigation or drinking water on streamflow; hence, it has the potential to be a useful tool in the management of water resources in groundwater-affected catchments. However, this comes at the expense of higher computational demand and more time consumption.

The Impact of Land Use/Land Cover Change (LULCC) on Water Resources in a Tropical Catchment in Tanzania under Different Climate Change Scenarios

“…From there, water might contribute as baseflow to the reach, move upwards as capillary rise due to LULC dependent water demand, or percolate deeper into the confined aquifer, where it is assumed to contribute to the regional water balance and is treated as being lost for the local catchment. However, both aquifers might contribute to the streamflow through different parameters [62]. A detailed model description is given by Arnold et al [56], Neitsch et al [58], and Arnold et al [63].…”

Modelling the Impact of Vegetation Change on Hydrological Processes in Bayin River Basin, Northwest China

“…A relatively well-established practice for this approach is to couple SWAT with a MOD-FLOW model by using the same temporal and spatial scales for both models, thereby allowing SWAT to calculate and input hydrological response unit (HRU)-based groundwater recharge data to the MODFLOW model and then allowing the MODFLOW model to calculate and return the groundwater flow between the aquifer and river to SWAT [15,16]. The SWAT-MODFLOW code developed by Bailey et al couples the most recent SWAT code with the MODFLOW-NWT code, which improves the solution of unconfined groundwater flow problems [16,18]. This version of the SWAT-MODFLOW model has recently been developed and is the most widely used.…”

Coupling of dynamic hydrological response units and SWAT-MODFLOW to model the impact of vegetation change on hydrological processes in an arid endorheic river watershed

“…A relatively well-established practice for the second approach is to couple SWAT with a MODFLOW model by using the same temporal and spatial scales for both models, thereby allowing SWAT to calculate and input HRU-based groundwater recharge data to the MODFLOW model, and then, allowing the MODFLOW model to calculate and return the groundwater ow between the aquifer and river to SWAT (Kim et al 2008;Bailey et al 2016). The SWAT-MODFLOW code developed by Bailey et al (2016) couples the most recent SWAT code with the MODFLOW-NWT code, which improves the solution of uncon ned groundwater ow problems (Liu et al 2019). This version of a coupled SWAT-MODFLOW model has been successfully applied in numerous countries and regions (Reshmidevi and Nagesh Kumar 2014;Liu et al 2019).…”

“…The SWAT-MODFLOW code developed by Bailey et al (2016) couples the most recent SWAT code with the MODFLOW-NWT code, which improves the solution of uncon ned groundwater ow problems (Liu et al 2019). This version of a coupled SWAT-MODFLOW model has been successfully applied in numerous countries and regions (Reshmidevi and Nagesh Kumar 2014;Liu et al 2019).…”