1. Lecture 2 - 1 ERS 482/682 (Fall 2002) Water balance ERS 482/682 Small Watershed Hydrology

2. Lecture 2 - 2 ERS 482/682 (Fall 2002) Fundamental Law Conservation of mass –Mass is neither created nor destroyed. S I Q

3. Lecture 2 - 3 ERS 482/682 (Fall 2002) Conservation of mass S I Q

4. Lecture 2 - 4 ERS 482/682 (Fall 2002) Conservation of mass S i q t i t q t S

5. Lecture 2 - 5 ERS 482/682 (Fall 2002) Conservation of mass S i q Application in hydrology: Water balance

6. Lecture 2 - 6 ERS 482/682 (Fall 2002) How much water is there? Figure 1.1 (Viessman and Lewis 1996)

7. Lecture 2 - 7 ERS 482/682 (Fall 2002) How much water is there? ComponentUSGSUNESCO (1990) Oceans97.09%93.93% Glaciers1.99%1.65% Groundwater0.62%4.12% Atmosphere0.29%0.001% Lakes0.012%0.016% Soil moisture0.004%0.005% Rivers0.0001% Total100%99.72%

8. Lecture 2 - 8 ERS 482/682 (Fall 2002) Water balance Figure 2-3 (Dingman 2002)

9. Lecture 2 - 9 ERS 482/682 (Fall 2002) Water balance 0 0 runoff Figure 2-3 (Dingman 2002)