Global Freshwater Availability

In a nutshell

• The HydroLand application is developed to provide high-resolution estimates for terrestrial freshwater availability, from global-to-local scale.

• The application makes use of the state-of-the-art hydrological model developed by Germany’s Helmholtz Centre for Environmental Research (UFZ) to calculate several variables related to freshwater availability like river discharge and soil moisture deficit.

• The information from this application provides insights into future flood and drought events.

Technical Overview

• Use Case Topic: Hydrology

• Scale of the Use Case: Global

• Policy addressed: Climate adaptation

• Providers: CSC-IT Center for Science

Challenge

Climate change is affecting the hydrological cycle and exacerbating water scarcity worldwide. Such water-related disasters as torrential rains, droughts and floods have been increasing both in frequency and intensity. With the raising hydro-hazard impacts, decision-makers require an improved scientific basis for preparation and response to the future extreme hydrological events.

DestinE Solution

The HydroLand application makes use of the mesoscale Hydrologic Model (mHM), a well-established model used operationally by the German Drought Monitor developed by UFZ.

Additionally, the mHM is used operationally by ECMWF in delivering the Copernicus Climate Change Service (C3S) to provide global seasonal hydrological forecasts and has also served for research, among others, about the impacts of climate change in flooding and droughts in Europe.

The application consists of a “wrapping” software built around the mHM model that makes the interface with the climate DT and adapts the model to the global scale with the spatial and temporal resolution required.

The mHM has been coupled to the ClimateDT workflow as a hydrologic impact model. In general, the mHM model simulates the following processes: canopy interception, snow accumulation and melting, soil moisture dynamics, infiltration and surface runoff, evapotranspiration, subsurface storage and discharge generation, deep percolation and baseflow, and discharge attenuation and flood routing on a global scale. To represent these terrestrial hydrologic processes as accurately as possible, and to ensure a reliable performance in ungauged basins, this model employs a multiscale parameter regionalization technique to obtain effective simulations at the scale of interest. The mHM model is driven by hourly or daily temperature and precipitation forcings. 

Impact

The HydroLand application will provide variables and indicators on soil moisture dynamics, and their consequent impacts on crop yields. It is a successor to the HydroRiver application, which focused on providing variables and indicators related to run-off and river discharge.

Indicators that are planned in the HydroLand are:

•  Aridity

• Soil moisture deficit

In addition to expanding the indicators and variables, HydroLand will go beyond the scope of HydroRiver by providing interactivity elements, namely, the addition of local setups to evaluate specific what-if scenarios. The what-if scenarios that are currently planned with our key users are:

1. “What is the impact of groundwater abstraction on the streamflow regime?”.
For this purpose, we will implement realistic groundwater abstractions within the impact model for a given catchment and analyze the impact on downstream river discharge. This will be co-designed with our key user from The German Technical and Scientific association for Gas and Water (DVGW).

2. “How will soil management practices affect soil water availability?”
For this scenario, we will modify the soil properties of the employed hydrologic model to reflect higher soil organic matter content (related to organic farming) and evaluate the effect on soil moisture deficits. This will then be used to calculate crop yields, and economic impacts of different soil management practices under a range of climate change projections. This will be co-designed with our key user from the European Environmental Agency (EEA).

The variables provided (river discharge, soil moisture deficits) will be used by the co-design partners in their own decision-making processes and provide related information to their stakeholders.

The variables and the indicators will be available globally with a spatial resolution of 5km and hourly temporal resolution (higher, if available). This is the highest resolution available within current hydrological impact models. Using the high spatial resolution, the application will be able to provide information for agricultural fields or river catchments that were previously too small to be resolved. The provision of hourly data will allow the application to resolve sub-daily flooding events (especially in the smaller catchments) which is going beyond the state-of-the-art. To fully capitalize on the high-resolution information, local setups will also be made (use shape files, and gauge location to define certain catchments/ regions of interest) in regions of interest for the users.

The co-design process will involve regular exchanges with the users to collect, implement and get feedback. In particular, this will gather feedback on the implementation of the requirements and discuss their feasibility, and implement in the application the requirements that are feasible.

The following schedule is foreseen for the implementation of the aforementioned features to the HydroLand application:

• 07/2024 – 12/2024: Technical readiness of the application to provide the variables and indicators, both globally and using local setups.

• 01/2025 – 06/2025: Separate setups for what-if scenarios, demonstrate and collect initial requests.

• 07/2025 – 12/2025: Demonstrate the first results from the new application (along with the what-if scenarios) and gather feedback.

• 01/2026 – 04/ 2026: Deliver the pilot scale implementation of the application.