SAJC Cluster 2 Lecture 6 Notes (Variations in Balance, Stores and Pathways in Drainage Basin System)

St Andrew’s Junior College H2 Cluster 2: Tropical Environments H2_Cluster 2 Lecture 6_2024/pg1 Lecture 6 Variations in Balance, Stores and Pathways in a Drainage Basin System KEY QUESTIONS**: ✓ How does the balance between input and output in the drainage basin system vary over time and space? ✓ How and why do stores in the drainage basin system vary in the tropics? ✓ How and why do pathways in the drainage basin system vary in the tropics? With the completion of this lecture, attached readings and tutorial, you should be able to understand the: • Variations in the balance between input and output over time and space in the tropics due to natural factors • Variations in stores in the drainage basin systems in the tropics over time and space due to natural and human factors • Variations in pathways in the drainage basin systems in the tropics over time and space due to natural and human factors **Note that these three key questions can only be answered using materials in both Lect 5 and Lect 6. Lecture Outline 6.1 Some basics: River Discharge and the Hydrograph Box 1: Different ways of interpreting river discharge 6.1.1 Components of the Hydrograph 6.1.2 Flashy vs Attenuated Hydrograph Factors affecting Drainage Basin Hydrology 6.2 Climate 6.2.1 Precipitation (a) Type (b) Seasonality and Amount (c) Intensity of Rainfall (d) Duration of Rainfall 6.2.2 Temperature Box 2: The effect of climate on the balance between input and output in a drainage basin 6.3 Geology 6.4 Soil Condition 6.5 Slopes of the Basin 6.6 Changes in Vegetation Cover

St Andrew’s Junior College H2 Cluster 2: Tropical Environments H2_Cluster 2 Lecture 6_2024/pg2 6.1 Some basics: River Discharge and the Hydrograph • An important aspect of hydrology is how a drainage basin (recall Lect 5) reacts to a period of rain. This is important because it can be used to predict flood risks (see Lect 7) and make the necessary precautions to avoid damage to property and loss of lives. • The response of a river can be studied by using the hydrograph, which is a means of showing the discharge of a river at a specific gauging station over time (see the small rectangle within the basin in Fig. 1). • Hydrographs show variations in the discharge of a river for a particular rainfall event and for a short period of time, usually hours or days (rather than weeks or months). • A hydrograph (see Fig. 3 next page) only describes what happened to the river discharge (see Box 1, and also Lect 5 Section 5.4.2). We need to be able to interpret the graph in order to explain what happened (to the other stores and pathways). In turn, this will help us to predict and forecast what might happen. Box 1: Different ways o