Passage I

A catchment (drainage basin) is a geographical area that drains to a given point along a river. Geologists studied catchments to understand relationships between climate, the quantities of water flowing through the catchments, and the erosion of the landscape.

Study 1

Eight catchments of similar area in different locations were chosen for study: 3 with limestone bedrock, 2 with quartzite bedrock, and 3 with granite bedrock. The dissolved load (weathered material carried in solution by water) and the solid load (solid particles carried by water) were measured for each catchment, in tons per square kilometer per year (tons/km²/yr). The rate at which the landscape was being eroded in each catchment, in centimeters per 1,000 years (cm/1,000 yr), was also measured. The results are in Table 1.

Study 2

Measurements were taken of the average annual air temperature, in degrees Celsius (°C), and the total annual precipitation, in cm, within the 8 catchments. The results are in Table 2.

Study 3

Geologists measured the discharge from each catchment. Discharge is the amount of water, in cubic meters per second (m³/sec), leaving a catchment. Annual precipitation from Study 2 was plotted against average discharge for the 8 catchments. The results are in Figure 1.