A proposed framework for disentangling land use change from other influences on catchment hydrology

Assessing the evolution of the hydrology of a catchment with multiple human influences over a long period remains an open question. Among these influences, changes in land use represent a potentially major driver of long-term hydrological change. Over the past centuries, many catchments have experienced significant transformations in land cover and water uses, leading to substantial consequences on flow regime and water balance components. In France, forested area has significantly increased over the past 150 years, and this land use long-term dynamics is reflected in Allier catchment (Massif Central) covering approximately 2700 km2. Originally dominated by 46% of cultivated land in the late 19th century, this catchment experienced a decline to 17% in the 21th century to the benefit of forests, which increased from 16% to 47% over the same period.

This study aims to analyze how long-term change in land use and other human activities has modified the catchment hydrology, and to quantify the relative contribution of each type of influence. The proposed methodology is based on hydrological modelling with J2000, a spatially distributed model that allows to reconstruct different water balance components, taking into account land use dynamics, water withdrawals, and reservoir management. Historical information from maps, archives, combined with hydroclimatic data, is used to define 3 30-year periods considered as stationary over a 150-year timeline. Model simulations are performed for each period considering uncertainty related to data availability and quality in order to evaluate changes in streamflow dynamics and water balance components.

This work presents the overall framework of a project aiming at representing historical long-term land use changes in hydrology modelling. By focusing on the historical evolution of land use, the project explores the impact of all anthropogenic drivers on the hydrology of the catchment. Results are expected to enhance the interpretation of past hydrological changes and to open perspectives for future modelling in anthropogenic catchments.