Hydrological Modeling to Assess the Efficiency of Groundwater Replenishment through Natural Reservoirs in the Hungarian Drava River Floodplain

Abstract

Growing drought hazard and water demand for agriculture, ecosystem conservation, and tourism in the Hungarian Drava river floodplain call for novel approaches to maintain wetland habitats and enhance agricultural productivity. Floodplain rehabilitation should be viewed as a complex landscape ecological issue which, beyond water management goals to relieve water deficit, ensures a high level of provision for a broad range of ecosystem services. This paper explores the hydrological feasibility of alternative water management, i.e., the restoration of natural reservoirs (abandoned paleochannels) to mitigate water shortage problems. To predict the efficiency of the project, an integrated surface water (Wetspass-M) and groundwater model (MODFLOW-NWT) was developed and calibrated with an eight-year data series. Different management scenarios for two natural reservoirs were simulated with filling rates ranging from 0.5 m3 s−1 to 1.5 m3 s−1. In both instances, a natural reservoir with a feeding rate of 1 m3 s−1 was found to be the best scenario. In this case 14 days of filling are required to reach the possible maximum reservoir stage of +2 m. The first meter rise increases the saturation of soil pores and the second creates an open surface water body. Two filling periods per year, each lasting for around 180 days, are required. The simulated water balance shows that reservoir–groundwater interactions are mainly governed by the inflow into and outflow from the reservoir. Such an integrated management scheme is applicable for floodplain rehabilitation in other regions with similar hydromorphological conditions and hazards, too.

Development of a Hydrogeological Conceptual Model of the Varaždin Alluvial Aquifer

“…In this study, the improved Wetspass-M model was used to explore the relationship between precipitation and recharge. The selection of the software was based on the data availability, and insights from previous investigations [9,12] where authors recommended using the Wetspass-M model for groundwater recharge assessment in developing groundwater flow models for the Drava basin. The presented research is the first study to evaluate the spatial distribution of long-term average groundwater recharge from precipitation in the Varaždin aquifer, and this information will serve as important input for developing numerical model, together with aquifer geometry and other boundary conditions.…”

Long-term Water Regime Studies of a Degraded Floating Fen in Hungary

“…Compared to previous research, our analysis offers two novelties: First, the studies focusing on wetland degradation and rehabilitation efforts in Hungary usually deal with riverine, riparian or saline/salt lake habitats [61,68], while the eco-hydrological investigation of fens is surprisingly under-represented. Second, most analyses use a method (see e.g [35,[69][70][71]), which cannot describe groundwater, soil moisture and surface water conditions simultaneously (only one or two of them), even though these have a strong, but not necessarily linear relationship. The presented research overcomes the latter methodological challenge through the example of a fen.…”

Perspectives of land evaluation of floodplains under conditions of aridification based on the assessment of ecosystem services

“…If we calculate with actual groundwater recharge ranging from 0 mm y -1 to 360 mm y -1 , the average being 241 mm y -1 (Salem, A. et al 2020), the annual specific recharge is 0 to 36,000 m 3 ha -1 , the average of which is 24,100 m 3 ha -1 . Modelling also revealed the spatial distribution of recharge (Figure 7).…”

“…et al 2002). Key sites of surface water/groundwater interactions (Griebler, C. and Avramov, M. 2015;Salem, A. et al 2020) are Groundwater Dependent Ecosystems (GDEs) like swamps and other wetlands (Eamus, D. et al 2016). The undrained surfaces of the Hungarian Drava Plain mapped within the framework of the Old Drava landscape rehabilitation programme (Trinity Enviro 2018) can be regarded as GDEs (Figure 1).…”