11 Snow and Ice
A. Rango', A.E. Walker 2 and B.E. Goodison 2
IUSDA Hydrology Laboratory, Agricultural Research Service,
Beltsville, Maryland 20705, USA
2Climate Research Branch, Atmospheric Environment Service, 4905
Dufferin Street, Downsview, Ontario M3H 5T4, Canada
11.1 Role of Snow and Ice
The occurrence of precipitation in the form of snow as opposed to rain typically
causes a change in how a drainage basin responds to the input of water. The reason
for the modified hydrological response is that snow is held in cold storage on a basin
for an extended period of time before it enters the runoff process. There is such a vast
difference in the physical properties of snow and other natural surfaces that the
occurrence of snow on a drainage basin can cause significant changes in the energy
and water budgets. As an example, the relatively high albedo of snow reflects a much
higher percentage of incoming solar shortwave radiation than snow-free surfaces
(80% for relatively new snow as opposed to roughly 15% for snow-free vegetation).
Snow may cover up to 53% of the land surface in the northern hemisphere (Foster and
Rango, 1982) and up to 44% of the world's land areas at anyone time. On a drainage
basin basis, the snow cover can vary significantly by elevation, time of year, or from
year to year. The Rio Grande basin at Del Norte, Colorado is 3419 km 2 in area and
ranges from 2432 m a.s.l. at the streamgage up to 4215 m a.s.l. at the highest point in
the basin. Figure 11.1 compares the snow cover depletion curves obtained from
Landsat data in 1977 and 1979 in elevation zones A (780 km 2 ; 2432-2926 m), B
(1284 km 2 ; 2926-3353 m), and C (1355 km 2 ; 3353-4215 m) in the Rio Grande basin.
In a period of two years from April 10, 1977 to AprillO, 1979, a great difference in
seasonal snow cover extent was experienced. Landsat data show that 49.5% or 1693
km 2 were covered by snow on April 10, 1977. Only two years later in 1979, 100% or
3419 km 2 were snow covered on April 10.
Snow cover and the equivalent amount of water volume stored supplies at least onethird of the water that is used for irrigation and the growth of crops worldwide
(Steppuhn, 1981). In high mountain snowmelt basins of the Rocky Mountains, USA,
as much as 75% of the total annual precipitation is in the form of snow (Storr, 1967),
and 90% of the annual runoff is from snowmelt (Goodell, 1966). The variation of
runoff depth can vary greatly from year to year for mountain basins because of
differences in the seasonal snow cover. In the Rio Grande basin at Del Norte, Colorado, the seasonal snow cover in the two years cited above, 1977 and 1979, produced
vastly different annual runoff depths of 7.8 cm and 35.36 cm for 1977 and 1979,
respec~ively (Rango and Martinec, 1997).
G. A. Schultz et al. (eds.), Remote Sensing in Hydrology and Water Management
© Springer-Verlag Berlin Heidelberg 2000
A. Rango', A.E. Walker 2 and B.E. Goodison 2
IUSDA Hydrology Laboratory, Agricultural Research Service,
Beltsville, Maryland 20705, USA
2Climate Research Branch, Atmospheric Environment Service, 4905
Dufferin Street, Downsview, Ontario M3H 5T4, Canada
11.1 Role of Snow and Ice
The occurrence of precipitation in the form of snow as opposed to rain typically
causes a change in how a drainage basin responds to the input of water. The reason
for the modified hydrological response is that snow is held in cold storage on a basin
for an extended period of time before it enters the runoff process. There is such a vast
difference in the physical properties of snow and other natural surfaces that the
occurrence of snow on a drainage basin can cause significant changes in the energy
and water budgets. As an example, the relatively high albedo of snow reflects a much
higher percentage of incoming solar shortwave radiation than snow-free surfaces
(80% for relatively new snow as opposed to roughly 15% for snow-free vegetation).
Snow may cover up to 53% of the land surface in the northern hemisphere (Foster and
Rango, 1982) and up to 44% of the world's land areas at anyone time. On a drainage
basin basis, the snow cover can vary significantly by elevation, time of year, or from
year to year. The Rio Grande basin at Del Norte, Colorado is 3419 km 2 in area and
ranges from 2432 m a.s.l. at the streamgage up to 4215 m a.s.l. at the highest point in
the basin. Figure 11.1 compares the snow cover depletion curves obtained from
Landsat data in 1977 and 1979 in elevation zones A (780 km 2 ; 2432-2926 m), B
(1284 km 2 ; 2926-3353 m), and C (1355 km 2 ; 3353-4215 m) in the Rio Grande basin.
In a period of two years from April 10, 1977 to AprillO, 1979, a great difference in
seasonal snow cover extent was experienced. Landsat data show that 49.5% or 1693
km 2 were covered by snow on April 10, 1977. Only two years later in 1979, 100% or
3419 km 2 were snow covered on April 10.
Snow cover and the equivalent amount of water volume stored supplies at least onethird of the water that is used for irrigation and the growth of crops worldwide
(Steppuhn, 1981). In high mountain snowmelt basins of the Rocky Mountains, USA,
as much as 75% of the total annual precipitation is in the form of snow (Storr, 1967),
and 90% of the annual runoff is from snowmelt (Goodell, 1966). The variation of
runoff depth can vary greatly from year to year for mountain basins because of
differences in the seasonal snow cover. In the Rio Grande basin at Del Norte, Colorado, the seasonal snow cover in the two years cited above, 1977 and 1979, produced
vastly different annual runoff depths of 7.8 cm and 35.36 cm for 1977 and 1979,
respec~ively (Rango and Martinec, 1997).
G. A. Schultz et al. (eds.), Remote Sensing in Hydrology and Water Management
© Springer-Verlag Berlin Heidelberg 2000