Hydrology Questions and Answers

Answer: A

20 ha-m is \(2 \times 10^{11}\) cm³.

A hectare-metre is the volume of water covering one hectare to a depth of one metre.

\[ \begin{aligned} 1 \text{ ha} &= 10^{4} \text{ m}^{2} \\ 20 \text{ ha-m} &= 20 \times 10^{4} \times 1 = 2 \times 10^{5} \text{ m}^{3} \\ 1 \text{ m}^{3} &= 10^{6} \text{ cm}^{3} \\ 2 \times 10^{5} \text{ m}^{3} &= 2 \times 10^{11} \text{ cm}^{3} \end{aligned} \]

\(2 \times 10^{9}\) and \(2 \times 10^{13}\) cm³ are each out by a factor of 100, the error made by using \(10^{4}\) or \(10^{8}\) cm³ per cubic metre.

Answer: A

The keyed term is Watershed.

A watershed is the area bounded by the ridge line or drainage divide, from which all runoff drains to a common outlet. It is the basic unit for planning soil and water conservation, so it is the term this definition is written for in soil conservation texts.

'Catchment' is used in much the same sense, especially in hydrology and for the area draining to a river gauging point or a reservoir, but the paper's soil conservation wording follows the watershed definition. A basin usually means the whole drainage area of a large river, made up of many watersheds.

Answer: D

A watershed reflects the interaction of all three, so the answer is All of the above.

How a watershed behaves, how much rain runs off, how fast and with how much sediment, depends on its soil (texture, depth, infiltration), its vegetation (cover that intercepts rain and slows runoff) and its topography (slope, shape and drainage pattern), all acting on the same rainfall. Watershed management works on these together.

Choosing only one of the three leaves out the others, which act jointly.

Answer: D

A watershed is all of these, so the answer is All of the these.

A watershed is a geohydrological unit: an area of land treated as one hydrological system. It is defined by water parting boundaries, the ridge lines that divide water flowing one way from water flowing the other. And it drains water to a common outlet, a stream, river or reservoir at its lowest point.

Each of the first three options states one part of the same definition, so none of them alone is complete.

Answer: D

All three describe a catchment, so the answer is All of the these.

A catchment is the area that collects water from rain and delivers it to a stream or reservoir. It has an areal extent (printed 'aerial'), measured in hectares or square kilometres, bounded by the drainage divide. And rain falling on it contributes overland flow, which runs off to the outlet.

Each option is one feature of the catchment, so choosing only one is incomplete.