Continuous Separation of Climate and Catchment Change Effects on Streamflow Alteration for Past and Future Using the Budyko Framework.

Abstract:

Understanding the separate effects of climate and catchment on changes in streamflow of a catchment is essential for water resources planning and management. Conceptual methods to quantify individual effects of climate and catchment changes on streamflow alteration based on the Budyko framework are widely used for their simplicity over physically-based hydrologic models that require calibration and validation. Such methods typically divide the historical records into two periods and study the movement of the catchment from one Budyko curve to another. They are, thus, sensitive to the choice of change point and record length, and cannot be used to decifer streamflow changes under climate or catchment influence in future. In this study, we use a regression-based method within the Budyko framework, to continuously separate the climate and catchment effects on streamflow using moving time windows. Three single-parameter Budyko-type equations and two disaggregation algorithms, namely, the sensitivity method and the decomposition method, are used to separate the effects of climate and catchment changes on streamflow. The regression relationship between the Budyko parameter and climate and catchment attributes is extrapolated to quantify the influence of climate and catchment changes on streamflow alteration for six plausible future scenarios that we derive based on realistic projected combinations of climate and landuse changes. Application of the proposed framework is carried out on a large watershed in India.

Keywords: Climate change; Catchment change; Budyko equation; Streamflow change separation; Future climate and landuse scenarios.