Q.Name the states which are drained by the river Yamuna.

Think of a river not as a single line on a map, but as a whole household. It has a head — the source in the mountains — arms and legs — the tributaries that feed it — and a mouth where it finally meets the sea. Everything that drains into that main channel, from the smallest seasonal stream to a mighty tributary like the Yamuna, forms one river system. For a student of commerce or humanities, the useful way to see a river system is as a drainage basin: a giant natural funnel that collects rainfall and snowmelt from a defined area and channels it downhill.

The precise meaning follows from that image. A river system includes the main river, all its tributaries (smaller rivers that join it) and distributaries (branches that split away from it near the sea), and the entire land area that contributes water to them. That land area is the catchment or basin. The ridge of higher ground that separates one basin from another is called a watershed or water divide. So when you hear "the Ganga river system," you are really talking about the whole Ganga basin — the Himalayas, the northern plains, and every stream in between that eventually flows into the Ganga.

Why does this matter beyond geography class? Because a river system is the backbone of the Indian economy and society. It provides drinking water, irrigation for agriculture, inland navigation, hydroelectric power, and fish. It also shapes settlement patterns — most of India's major cities and fertile agricultural belts sit on river plains. For a commerce student, think of the river system as a natural logistics network and a resource base: the cost of moving goods, the price of food, and the viability of industries all depend on how well a river system is managed. For a humanities student, rivers are cultural arteries — they carry religious practices, folklore, and historical trade routes.

India's river systems are usually grouped into two broad families, and the distinction is worth understanding because it explains their behaviour.

Himalayan rivers — the Indus, the Ganga, and the Brahmaputra — are perennial. They are fed by melting snow and glaciers as well as monsoon rain, so they flow throughout the year. They are young, energetic rivers that carve deep valleys in the mountains and then deposit vast amounts of silt on the plains. That silt is what makes the northern plains so fertile. But these rivers also change course frequently and cause devastating floods.

Peninsular rivers — the Godavari, Krishna, Kaveri, Mahanadi, Narmada, and Tapi — are mostly seasonal. They depend on monsoon rainfall, so they swell during the rainy season and shrink or even dry up in summer. They flow through older, harder rocks, so they have gentler gradients and do not carry as much silt. The Narmada and Tapi are exceptions: they flow westward into the Arabian Sea, while most peninsular rivers flow eastward into the Bay of Bengal. …