Mar 22, 2015

Movement of Snowmelt Water

Movement of snowmelt freshet occurs in two forms, vertical flow (infiltration, percolation) and horizontal flow (baseflow, overland flow). Liquid water percolate into lower layers in the snowpack when the total volumetric capacity of snowpack exceeds the water retention capacity. During the time of rapid snowmelt, overland runoff occurs when the infiltration rate becomes lower than snowmelt rate. Figure-4 shows the snowmelt freshet movement for different soil condition. Water follows horizontal unsaturated zone into stream (Hirashima et al., 2010). Canadian prairie is characterized as cold semi-arid climate with clay-rich soils and underlying glacial till. Snowmelt cause significant amount of runoff in upland. Prairie topography allow to hold a significant amount of water storage in the snowmelt period, but high evaporation and low precipitation dry up the soil by late fall. Upland snow accumulation, evaporation, antecedent soil moisture condition are important features for prairie snowmelt freshet movement (Shook et al., 2013; Winter & Rosenberry, 1995; Woo & Rowsell, 1993).

Energy Balance of Prairie Snowmelt

Snowmelt refers to the phase change of ice into water, which is involved with energy absorption. If net incoming radiation is negative then it refers as condensation and if net incoming radiation is positive it refers to melting. The net energy is the amount of energy used for phase change and transfer of radiation, convection, conduction, and advection flux into snowpack and the rate of change of internal energy. The amount of energy is estimated using simple empirical equation, which uses readily available measured meteorological variables.
Figure- Energy balance control volume (Pomeroy et al., 2007)

Snow-melting in Canadian Prairies

Figure- Prairie Ecozone boundary (Source: Esri Canada)
Snowmelt is one of the most significant hydrologic process in the Prairies. In hydrology, snowmelt refers to the melting and subsequent processes regarding snow. It is generally occurs at the end of winter, but mid-winter thaws and melt are not rare phenomena. Snowmelt freshet recharges soil moisture and groundwater and replenishes lakes, reservoir and river in Prairie region (Norum et al., 1976). Solar radiation energy flux plays a vital role for Prairie snowmelt (Male & Gray, 1981). Shortwave radiation is the dominant part of solar radiation energy and snow surface albedo controls the incoming radiation flux. Granger & Gray (1990) observed that albedo decrease of 0.0061 per day during pre-melt period and 0.071 per day during melt period in the prairies. The major features of snow melting in Prairies are-

Dec 21, 2014

Impacts of the freshet on ice cover breakup and resulting flood risk implications along the Upper Qu’Appelle River SK, Canada

During the ice breakup period in the Upper Qu’Appelle River (QAR), higher flows from the freshet can lead to ice jamming, overtopping of channel dykes and bridge decks and flooding of surrounding agricultural areas along the river The Qu’Appelle River dam regulates the flow from the Lake Diefenbaker to the downstream upper Qu’Appelle River (Figure-1). At the end of the winter season, ice thicknesses begin to reduce due to increased air temperatures and river water temperatures. Despite of drastic reductions in discharge prior to freshet runoff, mechanical ice breakup and jamming may still occur, depending on the amount of snow remaining in the basin, the strength competency of the ice cover and the rate at which air temperatures increase. Previous studies provide an indication of the severity of ice jamming and flooding that could occur at the most vulnerable section of the Upper Qu’Appelle River, between the PFRA Bridge and Tugaske Bridge bridges (Figure-3), where dyke crests and bridge decks are lowest in elevation relative to the channel.
Figure 1: The Qu'Appelle River

Nov 2, 2014

Mechanistic Linkage among Flow- Erosion- Suspended Sediment

Erosion is an action of fluid force which transport soil and rock from one location to another location. The driving forces for erosion are water, wind, ice and gravity. Soil loses its productivity as it loses the nutrient content, water storage capacity and organic content. Erosion due to hydraulic action is the most complex form of erosion. It occurs in land surface as well as riverbed and riverbanks. In the land surface, erosion initiates after fall of energized raindrop, which disrupts the soil integrity and cause loose soil. Both rain water and ice mass carry a lot of sediment and drains into the river. Runoff volume increases the amount of suspended sediment in the river. Based on river flow velocity, longitudinal slope, flow depth and bed roughness, riverbed also erodes and increases the amount of suspended sediment in the water.
Mechanistic linkage

Oct 15, 2012

Water Pricing Scenario in Bangladesh

Water supply in Bangladesh relies mainly on groundwater. In rural areas, more than 97% of the population relies on groundwater for its drinking water supply. In Dhaka, 82% of the water supply is abstracted from groundwater that is free of arsenic, while four surface water treatment plants provide the remaining 18%.[1] 99% of the urban population and 97% of the rural population had access to an improved source of water supply according to the Demographic and Health Survey of 2004. [2] 

Jun 18, 2012

Water Resources Management in Coastal Belt of Bangladesh: A Case Study of Chalna, Khulna

Bangladesh is facing the threat of global warming and sea level rise. This impact is severe in the coastal region. Proper water resources management is must in this problematic area. The coastal belt of Bangladesh is under a polder system. This system protects the mass people from great threats of natural and man maid calamities over the time. Human requirement of water is increasing day by day as life is getting better and better. So, a good management is required to augment the water resources.
River System around Chalna

Feb 20, 2012

Statistical Downscaling Method of Global Climate Model

General Circulation Models (GCMs) suggest that rising concentrations of greenhouse gases will have significant implications for climate at global and regional scales. GCMs are restricted in their usefulness for local impact studies by their coarse spatial resolution (typically of the order 50,000 km2) and inability to resolve important sub–grid scale features such as clouds and topography. So, downscaling techniques are used to bridge the spatial and temporal resolution gaps between what climate modelers are currently able to provide and what impact assessors require.
Downscaling Method