Listening to Each Other: A collaborative 2D hydraulic model to examine water and sediment availability in an inland delta

Abstract

The Saskatchewan River Delta is the largest inland freshwater delta in North America. The delta has been inhabited by humans for at least 7,000 years, but this complex social-ecological system has been disrupted by reduced water and sediment flows due to upstream water resource development. To follow up on previous on-land participant observations and semi-structured interviews that documented changes to the delta, a two-dimensional (2D) hydraulic HEC-RAS model was set up to collaboratively determine future scenarios. The model domain contains the main channel, floodplains, and hinterland areas while observed meteorological and hydrological data were used to force and calibrate the model. The model considered recent observations, examining scenarios with and without different mitigation measures to improve water availability and sediment transport within the delta. Modellers and residents jointly chose to focus on the strategic placement of weirs to raise the water depth in the delta's largest lake (Cumberland Lake) as a practical method. The model's ability to visualize and animate results has been serving as a boundary object, allowing crucial conversations about water to occur within and between community members and upstream water decision-makers. This paper discusses lessons learned from collaborative modelling that may provide insight beyond this important delta system.