1. **State the problem:** We need to estimate the Curve Numbers (CN) I, II, and III for a catchment area with given land use percentages and soil groups B and C. 2. **Given data:** - Cultivated land (Paddy): 30% soil group B, 45% soil group C, total 75% - Scrub Forest: 6% soil group B, 4% soil group C, total 10% - Waste land: 9% soil group B, 6% soil group C, total 15% 3. **Approach:** - CN II values are typically given in a table for each land use and hydrologic soil group (HSG). - CN I and CN III are adjustments of CN II for dry and wet conditions respectively. 4. **Assuming Table 1 values for CN II (typical values):** | Land Use | CN II Soil B | CN II Soil C | |----------------|-------------|-------------| | Cultivated land| 75 | 85 | | Scrub Forest | 55 | 70 | | Waste land | 70 | 80 | 5. **Calculate weighted CN II for soil group B:** $$CN_{II,B} = \frac{30}{45} \times 75 + \frac{6}{45} \times 55 + \frac{9}{45} \times 70$$ $$= \frac{30 \times 75 + 6 \times 55 + 9 \times 70}{45}$$ $$= \frac{2250 + 330 + 630}{45} = \frac{3210}{45} = 71.33$$ 6. **Calculate weighted CN II for soil group C:** $$CN_{II,C} = \frac{45}{55} \times 85 + \frac{4}{55} \times 70 + \frac{6}{55} \times 80$$ $$= \frac{45 \times 85 + 4 \times 70 + 6 \times 80}{55}$$ $$= \frac{3825 + 280 + 480}{55} = \frac{4585}{55} = 83.36$$ 7. **Calculate overall CN II for the catchment:** $$CN_{II} = \frac{45}{100} \times 71.33 + \frac{55}{100} \times 83.36$$ $$= 0.45 \times 71.33 + 0.55 \times 83.36 = 32.10 + 45.85 = 77.95$$ 8. **Estimate CN I and CN III:** - CN I (dry condition) is approximately 0.8 times CN II: $$CN_I = 0.8 \times CN_{II} = 0.8 \times 77.95 = 62.36$$ - CN III (wet condition) is approximately 1.2 times CN II: $$CN_{III} = 1.2 \times CN_{II} = 1.2 \times 77.95 = 93.54$$ **Final answers:** - CN I = 62.36 - CN II = 77.95 - CN III = 93.54