Advances in modelling large river basins in cold regions with
Modélisation Environmentale Communautaire - Surface and Hydrology
(MESH), the Canadian hydrological land surface scheme
Abstract
Cold regions provide water resources for half the global population yet
face rapid change. Their hydrology is dominated by snow, ice and frozen
soils, and climate warming is having profound effects. Hydrological
models have a key role in predicting changing water resources, but are
challenged in cold regions. Ground-based data to quantify meteorological
forcing and constrain model parameterization are limited, while
hydrological processes are complex, often controlled by phase change
energetics. River flows are impacted by poorly quantified human
activities. This paper reports scientific developments over the past
decade of MESH, the Canadian community hydrological land surface scheme.
New cold region process representation includes improved blowing snow
transport and sublimation, lateral land-surface flow, prairie pothole
storage dynamics, frozen ground infiltration and thermodynamics, and
improved glacier modelling. New algorithms to represent water management
include multi-stage reservoir operation. Parameterization has been
supported by field observations and remotely sensed data; new methods
for parameter identification have been used to evaluate model
uncertainty and support regionalization. Additionally, MESH has been
linked to broader decision-support frameworks, including river ice
simulation and hydrological forecasting. The paper also reports various
applications to the Saskatchewan and Mackenzie River basins in western
Canada (0.4 and 1.8 million km2). These basins arise
in glaciated mountain headwaters, are partly underlain by permafrost,
and include remote and incompletely understood forested, wetland,
agricultural and tundra ecoregions. This imposes extraordinary
challenges to prediction, including the need to overcoming biases in
forcing data sets, which can have disproportionate effects on the
simulated hydrology.