Use of point scale models to improve conceptual understanding in complex aquifers: An example from a sandstone aquifer in the Eden valley, Cumbria, UK

Abstract

Understanding catchment functioning is increasingly important to enable water resources to be quantified and used sustainably, flood risk to be minimized, as well as to protect the system from degradation by pollution. Developing conceptual understanding of groundwater systems and their encapsulation in models is an important part of this understanding, but they are resource intensive to create and calibrate. The relative lack of data or the particular complexity of a groundwater system can prevent the development of a satisfactory conceptual understanding of the hydrological behaviour, which can be used to construct an adequate distributed model. A time series of daily groundwater levels from the Permo-Triassic sandstones situated in the River Eden Valley, Cumbria, UK have been analysed. These hydrographs show a range of behaviours and therefore have previously been studied using statistical and time series analysis techniques. This paper describes the application of AquiMOD, impulse response function (IRF) and combined AquiMOD-IRF methods to characterize the daily groundwater hydrographs. The best approach for each characteristic type of response has been determined and related to the geological and hydrogeological framework found at each borehole location. It is clear that AquiMOD, IRF and a combination of AquiMOD with IRF can be deployed to reproduce hydrograph responses in a range of hydrogeological settings. Importantly the choice of different techniques demonstrates the influence of differing processes and hydrogeological settings. Further they can distinguish the influences of differing hydrogeological environments and the impacts these have on the groundwater flow processes. They can be used, as shown in this paper, in a staged approach to help develop reliable and comprehensive conceptual models of groundwater flow. This can then be used as a solid basis for the development of distributed models, particularly as the latter are resource expensive to build and to calibrate effectively. This approach of using simple models and techniques first identifies specific aspects of catchment functioning, for example influence of the river, that can be later tested in a distributed model.

How groundwater time series and aquifer property data explain heterogeneity in the Permo-Triassic sandstone aquifers of the Eden Valley, Cumbria, UK

“…They conclude that there are four hydrogeologic zones: (1) St Bees Sandstone, (2) Brockram, (3) silicified Penrith Sandstone and (4) central Penrith Sandstone, which is heavily influenced by interaction with rivers. These zones broadly align with the categories proposed in this research, with key differences in the St Bees Sandstone, which this research suggests is more heterogeneous than proposed by Lafare et al (2021), and zone 4 of Lafare et al (2021) which this work interprets to be a continuum between the agreed upon silicified Penrith Sandstone and Brockram zones, category A and C. The reasons for the differences in categorisation of the central Penrith Sandstone is that this work excluded boreholes near rivers, many of which are in the central Penrith Sandstone region (Fig. 1).…”

“…Previous research has evaluated groundwater hydrograph analysis against factors such as distance from rivers, depth to water table, and aquifer properties between lithological units (Lafare et al 2021). They conclude that there are four hydrogeologic zones: (1) St Bees Sandstone, (2) Brockram, (3) silicified Penrith Sandstone and (4) central Penrith Sandstone, which is heavily influenced by interaction with rivers.…”