Jaroslav Martinec

Parameter values for snowmelt runoff modelling

Parameters which appear frequently in snowmelt runoff models are analyzed with the aim of facilitating their evaluation. Results of runoff computations by the Snowmelt Runoff Model (SRM) carried out at various institutes, universities and agencies on 24 basins ranging in size from 0.77 to 4000 km2 and in elevation from 171 to 6000 m a.s.l. from 11 countries are reviewed. Based on this review, the physically and hydrologically understandable range of parameter values is assessed for the degree-day factor, runoff coefficient, temperature lapse rate, critical temperature (rain-snow), time lag, and recession coefficient. Consideration of SRM parameter values in these past applications may prove valuable for SRM applications on other basins and for initial selection of related parameter values in other snowmelt runoff models.

Average areal water equivalent of snow in a mountain basin using microwave and visible satellite data

Satellite microwave and millimeter-wave data have been used to evaluate the average areal water equivalent of snow cover in the mountainous Rio Grande basin in Colorado. Areal water equivalent data for the basin were obtained from contoured values of point measurements and from elevation-zone water volume values generated by a reliable snowmelt-runoff model using data on visible snow-cover extent. A significant relationship between the difference in brightness temperature at two different frequencies (37 and 18 GHz) and a basin-wide average snow-water equivalent value was obtained. This relationship and microwave observations were used to estimate the average areal water equivalent of the snow cover. >

Distributed mapping of snow and glaciers for improved runoff modelling

Runoff in glacierized alpine basins results from both seasonal snow cover and glacier melt. In this paper we present a case study for an improved runoff modelling of the basin Massa-Blatten, 196 km 2 , 1447-4191 m a.s.l. Using high resolution satellite sensors, it is possible to separately map snow cover and glacier areas. From the satellite data we derive depletion curves of snow covered areas in six elevation zones and determine when the glacier ice becomes exposed. We compute melt depths based on experimental measurements with regard to snow and ice. With the use of the snowmelt runoff model SRM-ETH, the following input components to runoff were determined: seasonal snow cover, including new snow falling on the snow covered areas; new snow falling on the snow-free area; rain; and glacier-ice. In order to evaluate the effect of the refined snow and glacier mapping on detailed melt computations, we compute the runoff resulting from i) the conventional runoff simulation based on integral snow and glacier areas, and ii) and advanced simulation taking into account the individual contributions from snow cover and glacier melt. We achieve a significant improvement of the accuracy of the runoff simulation.

Large-Area Deterministic Simulation of Natural Runoff from Snowmelt Based on Landsat MSS Data

This work sentnow a method of periodic evaluation of snow-covered areas by digital processing of Landsat data. Since the s cover was mapped for the first time in a large and morphologicomplex alpine basin, it was necessary to develop procedures to determine the snow coverage for partly clouded regions or for incomplete satellite scenes. The changing areal extent of the seasonal snow cover is an important variable for deterministic snowmelt runoff models. By using the SRM model, the natural runoff in the Rhein-Felsberg basin (3249 kM, 571-3614 m a.s.I) was simulated although the measured river flows are significantly influenced by artificial reservoir operation. Such simmulation would not be possible by calibration models that optimize the model parameters by the measured discharge.

Lake and river ice

The formation of lake and river ice is inevitable in northern environments. In many areas it brings shipping and transportation on inland waterways to a standstill for several months every year. More precise knowledge of ice thickness and extent can be used to extend the shipping season or to warn of danger due to the presence of unexpected ice. In addition to the impact on man, the presence or absence of ice on lakes and rivers can have a major influence on the ecology of a region. The presence of ice can govern the viability of fish life in a lake or river. For example, in northern Alaska, some lakes freeze completely to their beds and are not suitable for a fish population whereas other lakes do not, allowing fish to survive below ice during the winter. In addition, ice that forms unexpectedly in lakes and rivers in a particular year can kill existing fish populations.

Sensors and platforms

In this chapter, we will present a general description of most of the platforms and sensors that are referred to in this book. Sensors that operate in the gamma ray wavelengths to the very high frequencies (VHF) have been employed for remote sensing studies of ice and snow (Fig. 1.1). Although all objects emit radiation over all wavelengths, for most studies it is advantageous to use data from sensors operating in discrete portions of the electromagnetic spectrum. One must judiciously select the proper sensor to use for a particular analysis taking into consideration factors such as: wavelength, resolution and frequency and timing of ground coverage.

Applications of remotely derived snow data

One of the most important tasks of hydrology is river-flow forecasting. This is basic information for hydraulic engineering projects, such as water power generation, irrigation, municipal water supply, flood control and the planning of water management generally.

Alpine snow cover and glaciers in relation to altitude from advanced satellite monitoring

Advanced methods of Landsat-TM data processing were used to map periodically the seasonal snow cover and glaciers. The test basins are located in western, eastern and southern Swiss Alps. In the basins of the rivers Rhone at Sion (3371 km/sup 2/, 488-4634 in a.s.l.), Rhine at Felsberg (3249 km/sup 2/ 562-3614 in a.s.l.) and Ticino at Bellinzona (1515 km/sup 2/, 220-3402 in a.s.l.) relations were derived between the snow coverage and altitude at different stages of the snowmelt season. From these curves, the snow coverage at a desired altitude and the elevation of the statistical snow line at different dates can be read off. The decrease of the areal extent of snow on glaciers is slower in comparison with glacier-free areas. The snow line in the basin Rhone-Sion is lower than in the other basins throughout the season. Precision snow cover mapping and an adequate evaluation of data are needed for runoff modelling and winter tourism, in particular with regard to global warming.

An introduction to the optical, thermal and electrical properties of ice and snow

Remote sensing, defined as the measurement of properties of an object or feature on the Earth’s surface by an instrument that is not in direct physical contact with the object or feature, enables scientists to obtain information about ice and snow in visible, near-infrared, thermal infrared, microwave, and other wavelengths (Fig. 1.1). Surface, near-surface and deep, subsurface regions of ice and snow features can be analyzed using remote sensing techniques. In this chapter, the optical, thermal and microwave properties are briefly reviewed as they pertain to the remote sensing of ice and snow. More detailed descriptions of optical, thermal and electrical properties of ice and snow can be found in Hobbs (1974), Glen and Paren (1975) and ASP (1983).

Glaciers, ice caps and ice sheets

A glacier is an accumulation of ice and snow existing in varying degrees of compaction that moves under its own weight in response to gravitational force. Precipitation in the form of snow adds mass to the system while mass is removed through various ablation processes including surface melting, sublimation and calving of icebergs. In response to these mass inputs and outputs, the motion of the glacier redistributes this mass in an attempt to reach an equilibrium state.