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Modeling Snowmelt Runoff under Climate Change Scenarios
MDCs express the SCA as a function of cumulative snowmelt depth computed each
day. This relationship is used to derive the daily snow cover extent in the new climate (Van Katwijk et al. 1993; Rango and Martinec 1994; Harshburger et al. 2010).
Presently, a program subroutine has been added to current versions of SRM that
automatically modifies the snow cover depletion curves in accordance with the new
temperature and precipitation in the climate change scenarios (Rango and Martinec
1994; Martinec et al. 2008). Hence, it is no longer necessary to assemble a set of
MDCs in order to forecast the future course of the conventional depletion curves
(CDCs); instead, the SRM program uses the real seasonal snow cover of the present as monitored by satellites and models a climate-affected seasonal snow cover
that is used to evaluate the effect of a modified climate on runoff in mountain basin
(Martinec et al. 2005).
According to Wang and Li (2006), the possible changes of snowmelt runoff in the
upper Heihe watershed of northwestern China in response to a prescribed scenario
of climate warming of 4°C were successfully simulated using SRM. Similar to the
results of other studies, the results of the investigation indicated that the hydrograph
shifted earlier in the snowmelt season, yielding an increase in flows early in the melting season and a decline in flows later in the melting season (Wang and Li 2006).
Likewise, three mountains in Canada, United States, and Europe were selected by
Martinec and Rango (1989) to examine the effect of climate warming on snowmelt
runoff using the SRM simulation model. According to these studies, the runoff in
the snowmelt season was first simulated using the basic input variables, namely, precipitation, temperature, and SCA. Subsequently, the simulation was carried out using
the changed values of the basic variables as provided by the climate scenarios. The
various findings also indicate an increase in snowmelt season runoff and a change in
the appearance of SCA that receded much more rapidly under a warming climate.
More recently, Wang et al. (2010) have conducted a study on an inland river basin
in northwestern China using SRM with the aim of analyzing and forecasting the
responses of snowmelt runoff to climate change under a warming scenario. Warming
scenarios included annual increases of air temperature (+2°C, +4°C, and +6°C)
while precipitation values were unchanged. Results indicate a shift in the start time
of snowmelt runoff by about 6 and 9 days earlier with air temperature increase of
+4°C and +6°C, respectively. Earlier snowmelt runoff and larger discharge were also
observed with increasing air temperature; these results agree with previous research
findings (see Table 10.1), which also indicated earlier melting of mountain snowpacks, earlier dates for spring runoff, and a general change in the seasonal distribution of runoff (Barnett et al. 2005; Dettinger et al. 2004; Stewart et al. 2004). Other
studies also indicate increased winter and spring runoff and decreased summer runoff (Zhu et al. 2005) as observed by Wang et al. (2010).
SCA or its fraction is one of the three principle input variables required by SRM,
and whether measured or modeled, it plays an equally important role in energy balance snowmelt modeling. As noted above, temperature and precipitation, or perturbations of them relative to some base period, are generated by climate change
models; however, snow-covered fraction for climate change simulations must be
obtained elsewhere. The climate change module of SRM generates these based on
historical snow depletion curves. In order to generate these MDCs accurately, they
Modeling Snowmelt Runoff under Climate Change Scenarios
MDCs express the SCA as a function of cumulative snowmelt depth computed each
day. This relationship is used to derive the daily snow cover extent in the new climate (Van Katwijk et al. 1993; Rango and Martinec 1994; Harshburger et al. 2010).
Presently, a program subroutine has been added to current versions of SRM that
automatically modifies the snow cover depletion curves in accordance with the new
temperature and precipitation in the climate change scenarios (Rango and Martinec
1994; Martinec et al. 2008). Hence, it is no longer necessary to assemble a set of
MDCs in order to forecast the future course of the conventional depletion curves
(CDCs); instead, the SRM program uses the real seasonal snow cover of the present as monitored by satellites and models a climate-affected seasonal snow cover
that is used to evaluate the effect of a modified climate on runoff in mountain basin
(Martinec et al. 2005).
According to Wang and Li (2006), the possible changes of snowmelt runoff in the
upper Heihe watershed of northwestern China in response to a prescribed scenario
of climate warming of 4°C were successfully simulated using SRM. Similar to the
results of other studies, the results of the investigation indicated that the hydrograph
shifted earlier in the snowmelt season, yielding an increase in flows early in the melting season and a decline in flows later in the melting season (Wang and Li 2006).
Likewise, three mountains in Canada, United States, and Europe were selected by
Martinec and Rango (1989) to examine the effect of climate warming on snowmelt
runoff using the SRM simulation model. According to these studies, the runoff in
the snowmelt season was first simulated using the basic input variables, namely, precipitation, temperature, and SCA. Subsequently, the simulation was carried out using
the changed values of the basic variables as provided by the climate scenarios. The
various findings also indicate an increase in snowmelt season runoff and a change in
the appearance of SCA that receded much more rapidly under a warming climate.
More recently, Wang et al. (2010) have conducted a study on an inland river basin
in northwestern China using SRM with the aim of analyzing and forecasting the
responses of snowmelt runoff to climate change under a warming scenario. Warming
scenarios included annual increases of air temperature (+2°C, +4°C, and +6°C)
while precipitation values were unchanged. Results indicate a shift in the start time
of snowmelt runoff by about 6 and 9 days earlier with air temperature increase of
+4°C and +6°C, respectively. Earlier snowmelt runoff and larger discharge were also
observed with increasing air temperature; these results agree with previous research
findings (see Table 10.1), which also indicated earlier melting of mountain snowpacks, earlier dates for spring runoff, and a general change in the seasonal distribution of runoff (Barnett et al. 2005; Dettinger et al. 2004; Stewart et al. 2004). Other
studies also indicate increased winter and spring runoff and decreased summer runoff (Zhu et al. 2005) as observed by Wang et al. (2010).
SCA or its fraction is one of the three principle input variables required by SRM,
and whether measured or modeled, it plays an equally important role in energy balance snowmelt modeling. As noted above, temperature and precipitation, or perturbations of them relative to some base period, are generated by climate change
models; however, snow-covered fraction for climate change simulations must be
obtained elsewhere. The climate change module of SRM generates these based on
historical snow depletion curves. In order to generate these MDCs accurately, they