R. J. MacDonald

A Physically Based Daily Hydrometeorological Model for Complex Mountain Terrain

Abstract This paper describes the continued development of the physically based hydrometeorological model Generate Earth Systems Science input (GENESYS) and its application in simulating snowpack in the St. Mary (STM) River watershed, Montana. GENESYS is designed to operate a high spatial and temporal resolution over complex mountainous terrain. The intent of this paper is to assess the performance of the model in simulating daily snowpack and the spatial extent of snow cover over the St. Mary River watershed. A new precipitation estimation method that uses snowpack telemetry (SNOTEL) and snow survey data is presented and compared with two other methods, including Parameter-elevation Regressions on Independent Slopes Model (PRISM) precipitation data. A method for determining daily temperature lapse rates from NCEP reanalysis data is also presented and the effect of temperature lapse rate on snowpack simulations is determined. Simulated daily snowpack values compare well with observed values at the Many Gl...

Assessing the Potential Impacts of Climate Change on Mountain Snowpack in the St. Mary River Watershed, Montana

The St. Mary River watershed is an important international watershed that supplies irrigation water to large portionsofsouthernAlberta,Canada,andnorthernMontana.TheSt.MaryRiverisfullyallocatedandusers on both sides of the border are concerned regarding declining water supplies and increasing water demands under climatewarming.WatersupplyintheSt.MaryRiverislargelyfromsnowpackinthemountainousportionofthe watershed. This work assesses potential future changes in snowpack for the St. Mary River watershed under a range of general circulation model (GCM) derived future climate scenarios. The Generate Earth Systems Science (GENESYS) input spatial hydrometeorological model is used to simulate potential changes in spring snowpack,theonsetofmelt,andchangesinsnowextentforthree30-yrperiodscenteredaround2025,2055,and 2085. Results suggest an earlier spring and associated earlier onset of snowmelt and probable declines in maximumannual snow water equivalent(SWE)over theSt. MaryRiverwatershed arelikelyunder most future climate scenarios used in this study. However, results are responsive to future climate scenarios, where a scenario with substantial global greenhouse gas (GHG) emission controls shows a much lower decline in total accumulated SWE over theSt.MaryRiver watershed.Without substantialGHG emissionreductions, thestudy does show that there could be significant changes in snowpack over the St. Mary River watershed in the future.

Modelling the Potential Impacts of Climate Change on Snowpack in the North Saskatchewan River Watershed, Alberta

The North Saskatchewan River basin is a large watershed in central Alberta that provides water for a range of stakeholders, including large municipalities, agricultural operations, power generation, and resource extraction industries. This study assesses potential future changes in snowpack for the North Saskatchewan River watershed in response to a range of GCM-derived climate warming scenarios representing the periods from 2010-2039 (2020s), 2040-2069 (2050s), and 2070-2099 (2080s). The GENESYS (GENerate Earth SYstems Science input) spatial hydrometeorological model is applied to simulate potential changes in the zero degree isotherm, precipitation phase, watershed average maximum spring snow water equivalent (SWE), the dates of maximum and minimum SWE, and snowmelt period for these future climate scenarios. Climate warming is likely to result in an upwards shift in elevation of the zero degree isotherm, with a transition to more precipitation occurring as rain than snow. Although watershed average maximum SWE may not change under future conditions, the timing of spring snowmelt onset is likely to change under the future climate scenarios applied. It is demonstrated that increased air temperatures are expected to result in substantial changes in snowpack processes in the North Saskatchewan River watershed.

Adaptive Water Resource Planning in the South Saskatchewan River Basin: Use of Scenarios of Hydroclimatic Variability and Extremes†

The South Saskatchewan River Basin is one of Canadas most threatened watersheds, with water supplies in most subbasins over-allocated. In 2013, stakeholders representing irrigation districts, the environment, and municipalities collaborated with researchers and consultants to explore opportunities to improve the resiliency of the management of the Oldman and South Saskatchewan River subbasins. Streamflow scenarios for 2025-2054 were constructed by the novel approach of regressing historical river flows against indices of large-scale ocean-atmosphere climate oscillations to derive statistical streamflow models, which were then run using projected climate indices from global climate models. The impacts of some of the most extreme scenarios were simulated using the hydrologic mass-balance model Operational Analysis and Simulation of Integrated Systems (OASIS). Based on stakeholder observations, the project participants proposed and evaluated potential risk management and adaption strategies, e.g., modifying existing infrastructure, building new infrastructure, changing operations to supplement environmental flows, reducing demand, and sharing supply. The OASIS model was applied interactively at live modeling sessions with stakeholders to explore practical adaptation strategies. Our results, which serve as recommendations for policy makers, showed that forecast-based rationing together with new expanded storage could dramatically reduce water shortages.