4. Model development of the study area

A 10 by 10 gridded model of the study area, shown in Figure 3, includes precipitation, overland flow, unsaturated zone computations using the 1D Richards equation, ET using the Penman-Monteith Equation [39, 40], and 1D soil thermal computations using GIPL.

### 4.1 Initial soil moisture and soil temperature conditions

The initial temperature condition which is from CPEAK ground temperature thermistors at several depths on 2002-5-1, 1 AM, is shown in Figure 5. The numerical solution of the soil thermal state using quasi-linear heat conduction equation (Eq. (4)) employs this initial temperature condition of the soil profile.

Process Modeling of Soil Thermal and Hydrological Dynamics DOI: http://dx.doi.org/10.5772/intechopen.84414

The initial soil moisture condition obtained from Caribou-Poker Creeks Research Watershed for 2002-5-1, 1 AM [41], is shown in Figure 6. This initial soil moisture condition of the soil profile is employed by the numerical solution of the soil moisture, Richards equation, in the unsaturated vadose zone (Eq. (1)).

#### 4.2 Model parameter values

The model parameter values, distributed on grids horizontally and on soil layers vertically, for processes, such as overland flow, infiltration, evapotranspiration, and

Figure 5. Initial soil temperature condition.


Table 2. Soil thermal parameter values.

August [38]. Annual snowfall averages 1692 mm and commonly covers the ground from October to April [37]. The model employed CPEAK hydrometeorological data of the year 2002 included relative humidity (%), wind speed (kts), air temperature

Fairplay Silt loam and gravelly silt loam Moderately well drained

Soil series USDA texture Drainage

Olnes Silt loam and very gravelly silt loam Well drained

A 10 by 10 gridded model of the study area, shown in Figure 3, includes precipitation, overland flow, unsaturated zone computations using the 1D Richards equation, ET using the Penman-Monteith Equation [39, 40], and 1D soil thermal

The initial temperature condition which is from CPEAK ground temperature thermistors at several depths on 2002-5-1, 1 AM, is shown in Figure 5. The numerical solution of the soil thermal state using quasi-linear heat conduction equation

(Eq. (4)) employs this initial temperature condition of the soil profile.

), and tipping bucket

(°F), barometric pressure (in Hg), solar radiation (W h m<sup>2</sup>

4.1 Initial soil moisture and soil temperature conditions

4. Model development of the study area

Soil types and vegetation types of the study area.

Hydrology - The Science of Water

computations using GIPL.

Soil properties of the study area.

Figure 4.

Table 1.

112

rainfall rates and are available at http://www.lter.uaf.edu/data.

thermodynamics, are assigned based on the soil texture, shown in Figure 4a, and land use, shown in Figure 4b.

parameter values, representing the vegetation type of Figure 4(b), employed in the

All the parameter values defined in Table 5 were taken from the literature, which are also defined in the GSSHA wiki https://www.gsshawiki.com. The literature values for albedo and vegetation height are defined in Eagleson [47]. The literature values for canopy resistance are defined in Monteith [39]. The literature

The simulation period was from May 1st to May 31st of 2002, a period during which air temperatures are beginning to rise above freezing. The daily maximum soil temperature obtained from the simulation is compared with the observed one in Figure 7. Both the observed and simulated temperatures in Figure 7 is effective at a depth of 10 cm in the soil profile. The root-mean-square error for this daily maximum soil temperature was 4.7°C. It was found that the soil thermal

values for the transmission coefficient are defined in Sutton [48].

Process Modeling of Soil Thermal and Hydrological Dynamics

DOI: http://dx.doi.org/10.5772/intechopen.84414

Comparison of the time series of observed and simulated temperature.

Hydraulic conductivity under freezing and thawing soil active layer.

evapotranspiration process.

5. Result and discussion

5.1 Soil thermodynamics

Figure 7.

Figure 8.

115

Table 2 shows the soil thermal parameters with values, representing the silt loam [31, 42, 43] of Alaskan woodland and tundra ecosystem sites in permafrostactive region, employed in the thermodynamics process.

Table 3 shows Manning's roughness parameter values, representing the vegetation type of Figure 4(b) [44, 45], employed in the routing process.

Table 4 shows the soil hydraulic parameters with values, representing the silt loam ([46], https://www.gsshawiki.com) of Figure 4(a), employed in the infiltration and soil water retention process.

In this study, Penman-Monteith method was employed as evapotranspiration process. Table 5 shows the Penman-Monteith parameters that includes vegetation transmission coefficient (light penetration through canopy), values of land surface albedo, vegetation height (for aerodynamic resistance term), and vegetation canopy resistance (for stomatal control of the loss of water). Table 5 shows the ET


#### Table 3.

Manning's roughness values.


#### Table 4.

Soil parameter values for the Richards infiltration scheme.

