Maximum discharge from snowmelt in a changing climate

Abstract

Predicted changes in precipitation and air temperature patterns can lead to major alterations in timing and volume of mountain snowmelt runoff with a possible increased incidence of catastrophic events such as flooding and summer droughts. Here, the role of the temperature seasonal cycle and the relative duration of cold and warm seasons on the partitioning of precipitation into snow and rainfall, snow accumulation and melting dynamics, and the resulting mountain runoff formation are investigated. Using a minimalist analytical model, it is shown that while increased air temperatures reduce snow accumulation in the winter, thus reducing the subsequent snowmelt volumes, they also intensify the rate of snowmelt, thus increasing the discharge peaks per given accumulated snow. The main consequence is the existence of an optimal energy input for which the annual peak discharge reaches an absolute maximum. Such maximum separates a cold regime, where peak discharge is limited by slow melting dynamics, from a warm regime in which peak discharge is reduced by decreased winter snow accumulation.

Observed shift towards earlier spring discharge in the main Alpine rivers

“…(3), (4) and (5) can be solved analytically in a simplified ideal framework (Molini et al, 2011) obtaining an explicit formulation for the timing of peak discharge on total precipitation and temperature. Molini et al (2011) highlighted the role of temperature in determining snowmelt timing and the ratio of liquid to solid precipitation. An analytical solution is not possible when using real observations.…”

A Stochastic Conceptual Modeling Approach for Examining the Effects of Climate Change on Streamflows in Mountain Basins

“…Models with relatively simple structures have proven useful for exploring controls on snowmelt-runoff dynamics (Molini et al 2011). Our approach is intended to complement prior studies that have explored climate change deterministically by forcing hydrologic models with downscaled climate scenarios.…”

Tracer-based analysis of spatial and temporal variations of water sources in a glacierized catchment

“…The expected future retreat of mountain glaciers and earlier melt of snowpack is producing marked effects on the water balance. In future, mean annual runoff is expected to decrease but peak runoff is likely to increase (Molini et al, 2011), with seasonal shifts in the runoff regime (Kääb et al, 2007) and in the relative timing and contribution of the different water sources to baseflow, peak flow and groundwater. This raises major concerns about water supply security in mountain regions .…”