Country – France
Context of the case study on the impacts of climate change in the Lot watershed
The Lot catchment area is experiencing, during the low water season, a quantitative shortage of water resources which results in an imbalance between available volumes and needs. Scientific studies agree on the climatic and hydrological consequences of climate change in the Adour-Garonne watershed, with an intensification of extreme events. The SDAGE Adour-Garonne emphasizes in particular the need to sustainably address structural water deficits by integrating the issues of climate change. In response to these alarming findings, the EPTB of the Lot launched a prospective study in 2023 with the objectives of understanding the issues and anticipating future impacts on the Lot basin.
Objective of climate change impact studies
This study aims to analyze and diagnose the major trends in climate change and water resources on the Lot basin in order to build a management strategy for water resources and aquatic environments in the face of climate change.
Phase 1: Production of territorial hydroclimatic projections
The first phase of the study on the impacts of climate change aims to improve knowledge about changes in climate and water resources in the Lot watershed. It aims to formalise, exploit and disseminate the latest information on these developments, building on existing databases.
Mandated for this mission, Hydroclimat ensures the transfer, analysis and interpretation of climate and hydrological data. The challenge is to support local actors in their understanding of current and future changes, in order to facilitate a territorial diagnosis and the implementation of adaptation strategies.
For this, the study of the impacts of climate change is based on several axes: analysis of climatic and hydrological trends observed since 1960, the identification of major future developments and the definition of specific indicators in consultation with water stakeholders in the territory. The data are studied over a retrospective period (1976-2005) and over prospective horizons (2021-2050, 2041-2070 and 2071-2100), taking into account two climate scenarios: RCP4.5 (intermediate scenario) and RCP8.5 (pessimistic scenario).
The results will allow a better understanding of the evolution of precipitation, temperature, evapotranspiration and river flows at the scale of the 22 sub-watersheds of the Lot. The objective is to make this information accessible and understandable for decision-makers, so that they can integrate this knowledge into their adaptation policies.
Phase 2: Diagnostic support for low tide
The future of the Lot Domanial drainage support is based on the strategic management of water reserves by the Territorial Public Establishment of the Basin (EPTB) and EDF. Thanks to the hydroelectric developments of the Lot-Truyère chain, flow guidelines are established to guarantee the supply of drinking water, irrigation, industry, navigation and the quality of aquatic environments. Each year, a volume of water of up to 33 million m3 is mobilized according to needs, with an average destocking of 17 million m3 over the summer period. Since 2019, an inter-basin solidarity protocol with the Garonne river reinforces the strategic importance of this management.
The study to assess the impacts of climate change conducted by Hydroclimat analyses the evolution of water deficits at different future horizons under climatic stress and proposes new scenarios to adapt tidal management to future resources and uses.
Phase 3: Vulnerability Diagnosis
This phase builds on the conclusions of previous phases to carry out an in-depth diagnosis of the vulnerability of territories to the impacts of climate change. Conducted by Auxilia, this analysis is based on the study of three key themes, evaluated through 11 non-climate indicators that can accentuate risks.
The three themes examined are:
- Water availability: extreme fluctuations in water resources and land degradation
- Water quality: deterioration of water resources and increased risk of contamination
- Biodiversity and aquatic environments: alteration of ecosystems and decline in biodiversity
This analysis allows a better understanding of the interactions between climate change and territorial dynamics, identifying the most vulnerable areas in the Lot basin. Thanks to an approach combining climate data and non-climate indicators, it offers a global view of risks and allows the targeting of priority actions to strengthen the resilience of the territories of the Lot basin. This will make it easier to analyze the impacts of climate change.
What are the expected results?
Following this study of the impacts of climate change on the Lot watershed, three detailed documents were developed to facilitate the appropriation of the results of the hydro-climatic diagnosis and vulnerability diagnosis. These tools also help identify the main issues related to climate change and support stakeholders in implementing adapted strategies. Decision-makers therefore have a clear and detailed strategy to respond to climate challenges, based on three main axes:
- Protecting aquatic environments: ensuring their resilience to climate impacts while preserving their biodiversity.
- Sustainable management of water uses: ensuring a balance between the needs of different sectors (agriculture, industry, drinking water supply) and the availability of resources.
- Preparing for future scenarios: integrating climate uncertainties into local policies, adopting an adaptive approach.
This study is an essential decision-making tool for local actors, accompanying them in the development of adaptation policies and sustainable management of natural resources.
An integrated approach to regional resilience to climate change
This climate change impact study project is part of a proactive approach to transform climate issues into opportunities for innovation and sustainability. By combining the expertise of our climate change data and water resources data, we provide tailor-made solutions to support local stakeholders in their transition towards resilient management of water resources. Thanks to a study of the impacts of climate change, it is easier for them to make decisions in order to anticipate and reduce as much as possible the impacts of climate change on the Lot basin.
Thanks to this strategy, regions will be better prepared to cope with the impacts of climate change, while making the most of ecosystems as essential levers for mitigation and adaptation.