A farmer in a tropical region depends on a nearby river and a borehole for irrigation water. In recent years, the river has been drying up during the dry se...

(a) Two sources of surface water that could supply a river: [2]

1. Rainfall (precipitation) collecting in streams and tributaries that flow into the river from the surrounding catchment area. [1]
2. Springs, where groundwater emerges naturally at the surface and feeds into the river channel. [1]

Other acceptable answers: melting snow or ice from higher ground; runoff from surrounding land.

(b) How water from precipitation enters the ground and reaches an aquifer: [4]

1. Rainfall lands on the soil surface. [1]
2. Water infiltrates into the soil through pore spaces between soil particles, moving downward under the pull of gravity. [1]
3. It then percolates deeper, passing through cracks, joints and gaps in the rock layers below the soil. [1]
4. The water accumulates in a porous and permeable rock layer called an aquifer, where it is stored as groundwater below the water table. [1]

(c) Two reasons why the river may be drying up during the dry season: [4]

1. Reduced rainfall: changing weather patterns or drought conditions mean less precipitation falls in the river's catchment area during the dry season. [1] With less water entering the system, river flow declines. [1]
2. Increased upstream abstraction: more water is being extracted upstream by other farmers or communities for irrigation and domestic use. [1] This reduces the volume of water reaching downstream sections of the river. [1]

Other acceptable answers: deforestation increasing runoff and reducing groundwater recharge; loss of riparian vegetation increasing evaporation.

(d) Three water conservation practices the farmer could use: [3]

1. Mulching: applying a layer of organic material (straw, crop residues) or plastic sheeting to the soil surface around crops to reduce evaporation. [1]
2. Drip irrigation: using drip lines that deliver water directly to the root zone of each plant, minimising waste compared to flood or sprinkler irrigation. [1]
3. Planting windbreaks: rows of trees or tall shrubs planted along field edges reduce wind speed, which lowers the rate of evaporation and transpiration from the crops. [1]

Other acceptable practices: scheduling irrigation for early morning or evening; rainwater harvesting.

(e) How building a small reservoir could help during the dry season: [2]

1. The reservoir stores water collected from surface runoff during the rainy season, when water is abundant. [1]
2. This stored water can be used for irrigation during the dry season when the river level drops and the borehole water table falls, providing a reliable backup water supply. [1]