Set II Soil Water Gravitational potential is determined by the height of the points above the reference level. Capillary or matric potential must be measured and, therefore, is provided. Total potential energy is simply the sum of the component potentials. Water flows from higher energy to lower energy. The Gradient is determined by the difference in total energy between the two points divided by the distance between the points. Multiplying the gradient by the hydraulic conductivity yields the total flow. 1. Soil water potentials: 100 cm 75 cm A 50 cm 25 cm B 0 cm reference Note the soil diagram above. Point A is at 75 cm; point B is at 25 cm above the reference. The capillary potential energy at point A is -100 cm. The capillary potential energy at point B is -200 cm. What is the total potential energy at point A? _____________________________ ` What is the total potential energy at point B? _____________________________ Will water flow between the points? ____________________________________ If so, in what direction? _______________________________________________ What is the gradient between the two points? ____________________________ If K = 10 cm/hr, determine the flow, Q between the points._________________ 2. Soil Water potential: 400 cm 300 cm A 200 cm 100 cm B Reference Note the soil diagram above. Point A is at 300 cm; point B is at 100 cm. The capillary potential energy at point A is -400 cm. The capillary potential energy at point B is -300 cm. Note the reference level on the Figure What is the gravitational potential energy at point B? _____________ What is the height of point A above the reference level? ____________ What is the gravitational potential energy at point A? _____________ What is the total potential energy at point A? _____________________ ` What is the total potential energy at point B? _____________________ Will water flow between the points? ____________________________ If so, in what direction? ______________________________________ What is the gradient between the two points? _____________________ If K = 5 cm/hr, determine the flow, Q between the points. ___________ 3. Soil Water potential: 400 cm 300 cm A B 10 cm 20 cm Reference 200 cm 100 cm Note the soil diagram above. Points A and B are at 300 cm. The capillary potential energy at point A is -200 cm The capillary potential energy at point B is -100 cm. Note the reference level for gravitational Potential. Will water flow between the points? __________________________________1pt If so, in what direction? ________________________1pt What is the difference in total potential energy between the points? ________1pt What is the gradient between the two points?___________________________ 2pts If K = 10 cm/hr, determine the flow, Q between the points. _______________ 2 pts