CZECH GEOLOGICAL SERVICE, RE-BALANCE OF GROUNDWATER RESERVES IN SELECTED AREAS OF THE CZECH REPUBLIC
The objective of the project was to re-evaluate the natural sources of groundwater in 56 selected hydrogeological regions which – combined – account for approximately one third of the area of the Czech Republic. The project comprised 11 activities in total, from the literature search, through remote, geophysical and field survey, drilling operations, assembly of the conceptual hydrogeological model, hydrological models, to the promotion of the project results. Hydraulic (flow) models were the subject of Activity 7. Groundwater Consulting Services s.r.o. was responsible for assembling the hydraulic models for the following hydrogeological regions:
- Quaternary: 1510 Quaternary of the Oder River, 1520 Quaternary of the Opava River, 1610 Quaternary of the Upper Morava River, 1621 Plio-Pleistocene of the Upper Moravian Valley – north, 1622 Plio-Pleistocene of the Upper Moravian Valley – south, 1623 Plio-Pleistocene of Blaty a 1624 Quaternary of the Valová, Romže and Haná Rivers;
- Neogene: 2212 Oderská Gate and 2220 Upper Moravian Valley;
- Cretaceous: 4231 Ústecká Syncline in the Orlice basin, 4232 Ústecká Syncline in the Svitava basin, 4270 Vysokomýtská Syncline and 4280 Velkoopatovická Cretaceous;
- Older: 6640 Mladečský Karst.
The methodology itself consisted of three stages, within which the following activities were implemented: steady state and transient calibration, sensitivity analysis, variant steady state simulations aimed at optimisation of draw off and use of area or transient simulations in average and forecast conditions of climate changes. The MODFLOW code has been used for mathematical modelling.
NAMWATER LOWER KUISEB RIVER AQUIFER
The Lower Kuiseb River Aquifer (project area) is located within the Kuiseb catchment in the Erongo Region, southwestern Namibia. The Kuiseb River is a 560 km long ephemeral river with a catchment size of 14 700 km2 and discharges into the Atlantic Ocean near Walvis Bay after crossing the Namib Desert. The study area in the lower part of the Kuiseb catchment forms a triangular fan with dune covered paleochannel branches. The north-eastern boundary of the area is the Kuiseb River bed, the southern boundary is formed by a step-fault approximately along the Anichab-Gobabeb line. The Kuiseb aquifer is the main groundwater supply scheme for the area and in order to ensure that groundwater resource is properly utilized and managed for current and future planning, a numerical groundwater model was constructed. The ultimate purpose of the numerical groundwater model is to enable NamWater and the department of Water Affairs is to use it as a management tool to enhance the sustainable utilization of groundwater resources and the conservation of associated ecological systems.
The project objectives were to re-assess the aquifer system to determine the long-term sustainable and optimal utilization of the aquifer. These objectives were achieved through the collation of existing and new data to update, simulate and predict Lower Kuiseb River aquifer behaviour in response to abstraction. Once the model was calibrated a number of management scenarios were simulated. Predictive simulations were divided into two general scopes: (1) Predictive simulations focusing on aquifer response to specific setup of groundwater recharge and abstraction. These simulations were compiled in MODFLOW, the same code that was used during the model calibration, and (2) Predictive simulations focusing on SFI response to specific setup of groundwater recharge and abstraction. The MODFLOW and SEAWAT codes have been used for mathematical modelling.