Experimental field studies are crucial to understanding hydrological processes. Studies at the plot-, hillslope-, or small catchment-scales have helped us to understand how water flows toward the stream network of larger catchments. However, little of this detailed knowledge is used in hydrological models because the calibration of simple models already leads to good runoff simulations. Furthermore, not all hillslope locations contribute equally to catchment runoff and in some cases, hillslopes or specific hillslope locations may seem irrelevant for the catchment scale runoff response, at least until a certain threshold is crossed. It is essential to consider these thresholds because climate or land use change may cause them to be passed more frequently in the future, so models based on historic runoff data might no longer accurately predict the catchment runoff response. In this talk, I will provide examples of such thresholds and discuss the need to consider connectivity between landscape elements when interpreting the streamflow or stream chemistry response at the catchment scale. In doing so, I will highlight the need to understand hydrological processes at the plot and hillslope scales for predicting catchment-scale runoff, even if these processes may seem irrelevant at first.

How to cite: van Meerveld, I.: The (ir)relevance of plot- and hillslope scale processes for catchment runoff, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6684, https://doi.org/10.5194/egusphere-egu24-6684, 2024.

Contrary to widespread belief, it is well known since ancient Greece that rivers flow most of the time because they receive groundwater discharge. However, it is less widely known that rivers are losing their base flow because of aquifer overexploitation and, even less, the intimate link between ground and surface water processes. I review the processes that control water quality, from pore scale biofilms to hyporheic exchange, and runoff generation. While there is a broad understanding of these processes, I argue that the way they are represented in models is poor. As a result, water management and regulations tend to ignore them. Specifically, managed aquifer recharge is currently hindered by EU regulations. Yet, it remains the only practical management strategy to reverse groundwater (and, thus, the loss of river base flow and ecosystem services). I find it paradoxical that, while a lot of effort is devoted to global "accounting", we are deemphasizing the river basin scale, within which most water management relevant processes occur (ironically, the only management relevant trans-basin processes, i.e., the recycling of moisture, is equally ignored). I conclude for a renewal od the old call for close interaction between surface and groundwater hydrologists.

How to cite: Carrera, J.: From the pore to the catchment-scale: a discussion of groundwater processes and modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20252, https://doi.org/10.5194/egusphere-egu24-20252, 2024.

Freshwater resources are increasingly under threat from climate change and increasing water demand. Catchment-scale hydrological models generate hydrological projections that underpin the management and sustainability of future water resources. Yet, water systems are increasingly interconnected across catchment boundaries through nationally strategic water supply schemes that aim to ensure a reliable supply of water in a changing climate.

In this presentation, we draw on a range of studies from across Great Britain to discuss the challenges and complexities of hydrological modelling for future water resources management from catchment to national scales. We focus on interconnected water systems including catchments impacted by (1) inter-catchment groundwater flows and (2) water transfers via reservoirs, abstractions and wastewater treatment plants. For the human-impacted catchments, we identify where and when representing human interactions are important for robust streamflow projections. As water systems become more interconnected in space and time, we highlight the need to move beyond the catchment scale for future water resources management.

How to cite: Coxon, G., Murgatroyd, A., Pianosi, F., Salwey, S., Wendt, D., and Zheng, Y.: Modelling future water resources in interconnected water systems: are catchment scales relevant?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5377, https://doi.org/10.5194/egusphere-egu24-5377, 2024.

Groundwater is the largest accessible freshwater resource on earth and is critical for people and the environment. In many regions around the world, sectoral water demands exceed the availability of surface water and groundwater is being pumped. Irrigation stands out as the largest groundwater user worldwide, with ca. 40% of current irrigated agriculture relying on groundwater. In many heavily irrigated regions, groundwater abstractions surpass replenishment, resulting in often severely declining groundwater levels. This leads to groundwater depletion, reduced streamflow, drying of wells and springs, land subsidence, saltwater intrusion, and deteriorating surface water quality due to reduced pollutant dilution.

In the coming decades, global food demands will increase, driven by a growing world population and socio-economic development. A major challenge lies ahead in how to sustainably ensure sufficient regionally and globally available food. It is inevitable that agriculture will increasingly rely on groundwater to support the required increase in crop production, but the extent to which this groundwater can be extracted sustainably from a quantity and quality perspective is still largely unknown.

In this talk, the latest advances in our model development will be presented, focussing specifically on linking groundwater dynamics, surface water interactions, and crop production at both global and regional scales. A specific focus lies on connecting global and regional scales and approaches to better understand the impacts and trade-offs related to global change. In addition, attention will be given to the development of regionally relevant adaptation strategies for sustainable groundwater use worldwide. 

How to cite: de Graaf, I.: Navigating global challenges: development and application of a coupled groundwater and crop growth model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20946, https://doi.org/10.5194/egusphere-egu24-20946, 2024.