Drainage

This geography chapter studies the drainage of India, the river systems of an area. A drainage basin is the area drained by a single river system, and an upland separating two basins is a water divide. You will learn drainage patterns: dendritic, trellis, rectangular and radial. Indian rivers form two groups. The Himalayan rivers, the Indus, Ganga and Brahmaputra, are perennial, fed by rain and melting snow, and form meanders, oxbow lakes and large deltas. The Peninsular rivers are mostly seasonal, and most, such as the Mahanadi, Godavari, Krishna and Kaveri, flow east into the Bay of Bengal, while the Narmada and Tapi flow west through rift valleys. You will study each river system: the Indus and its tributaries Satluj, Beas, Ravi, Chenab and Jhelum; the Ganga, formed by the Bhagirathi and Alaknanda at Devprayag, with tributaries such as the Yamuna, Kosi and Son; and the Brahmaputra with Majuli island. You will also study lakes such as Wular, Sambhar and Chilika, the role of rivers in the economy, and river pollution.

Detailed Worksheet: Drainage Section A - Definitions (10 marks) 1. What is a drainage basin? What is a water divide? Give an example of each. (2 marks) 2. Name four drainage patterns. (2 marks) 3. What is a delta? How is it different from an estuary? (2 marks) 4. Why are Himalayan rivers perennial while most Peninsular rivers are seasonal? (2 marks) 5. What is an oxbow lake? How is it formed? (2 marks) Section B - Calculations and Applications (15 marks) 6. Between Ambala and the Sundarbans, a distance of about 1,800 km, the land falls by only about 300 m. Find the average gradient in metres per km and km per metre. What does this tell you about the speed of rivers in the plains? (3 marks) 7. Approximate lengths: Indus 2,900 km, Ganga over 2,500 km, Brahmaputra 2,900 km, Godavari 1,500 km, Krishna 1,400 km, Narmada 1,312 km, Mahanadi 860 km, Kaveri 760 km. Arrange the Peninsular rivers in decreasing order of length. How many times longer is the Godavari than the Kaveri, correct to one decimal place? (3 marks) 8. Under the Indus Water Treaty of 1960, India can use about 20% of the total water carried by the Indus river system. If the system carries about 170 billion cubic m of water a year, how much can India use? (3 marks) 9. Classify these rivers as Himalayan or Peninsular and state the direction of flow for the Peninsular ones: Satluj, Narmada, Kosi, Godavari, Tapi, Gandak, Kaveri, Mahanadi, Chambal. (3 marks) 10. A city on a river discharges 600 million litres of sewage a day. Only 40% is treated. How much untreated sewage enters the river daily? If treatment capacity is raised by 150 million litres a day, what percentage will be treated? (3 marks) Section C - Diagrams (10 marks) 11. On an outline map of India, mark the rivers Indus, Ganga, Brahmaputra, Narmada, Tapi, Godavari, Krishna and Kaveri. (4 marks) 12. Draw sketches of dendritic, trellis, rectangular and radial drainage patterns. (3 marks) 13. On an outline map of India, mark the lakes Wular, Sambhar, Chilika, Pulicat and Kolleru. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. Compare Himalayan and Peninsular rivers on five points: source, nature of flow, erosion, valleys and deltas or estuaries. (5 marks) 15. Describe the course of the Ganga from its source to the sea, naming its major tributaries from the north and the south and the delta it forms. (5 marks) 16. Explain the causes of river pollution in India. Describe the steps taken, such as the Namami Gange programme, and suggest three things citizens can do. (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Use outline maps where asked and show working for data-based questions.