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Evapotranspiration Remote Sensing and Modeling Part 5

Tham khảo tài liệu 'evapotranspiration remote sensing and modeling part 5', khoa học tự nhiên, công nghệ sinh học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Using Soil Moisture Data to Estimate Evapotranspiration and Development of a Physically Based Root Water Uptake Model 109 Sensor Location Below Land Surface cm 0s 0r cm-1 n - Ks cm hr 10 35 3 0.03 1.85 4.212 20 35 3 0.07 1.70 2.520 30 32 3 0.07 1.70 2.520 50 34 3 0.03 1.60 0.803 70 31 3 0.03 1.60 0.005 90 32 3 0.05 1.90 0.005 110 32 3 0.05 1.80 0.005 150 30 3 0.05 1.80 0.001 a Sensor Location Below Land Surface cm 0s 0r cm-1 n - Ks cm hr 10 38 3 0.02 1.35 0.0100 20 34 3 0.03 1.35 0.0100 30 31 3 0.03 1.35 0.0100 50 31 3 0.07 1.90 0.0100 70 31 3 0.2 2.20 0.0100 90 31 3 0.2 2.20 0.0004 110 33 3 0.2 2.20 0.0004 150 35 3 0.2 2.10 0.0012 b Table 2. Soil parameters for study locations in a Grassland and b Forested area. Once the soil parameterization is complete root water uptake from each section can be calculated. For any given soil layer in the vertical soil column Figure 8 above the observed water table observed water content and Equation 11 can be used to calculate the hydraulic head. For soil layers below the water table hydraulic head is same as the depth of soil layer 110 Evapotranspiration - Remote Sensing and Modeling below the water table due to assumption of hydrostatic pressure. Similarly using Equation 12 hydraulic conductivity can be calculated. Hence at any instant in time hydraulic head in each of the eight soil layers can be calculated. To determine total head gravity head which is the height of the soil layer above a common datum has to be added to the hydraulic head. Sensor @ 10 cm À Sensor @ y À 20 cm Sensor @ 30 cm Sensor @ 1 L 50 cm r Sensor @ 70 cm i Sensor @ k 90 cm V Sensor @ VT 110 cm Sensor @ 150 cm Fig. 8. Schematics of the vertical soil column with location of the soil moisture sensors and water table. To quantify flow across each soil layer Darcy s Law Equation 7 is used. Average head values between two consecutive time steps are used to determine the head difference. Also flow across different soil layers is assumed to be occurring between