Catchment Hydrology

Why study hydrology? They cause natural disasters such as flooding with historical events like the 1931 flood of Huang He (Yangtze & Hai), which killed 1 to 2 million people. Or the 1887 Huang He flood killed 0.9 to 2 million people. Or the 1556 Shaanxi earthquake, flooding was the most prominent killer (830,000 people died). Flooding will be the most famous form of climate change, as it changes regional weather patterns and how it falls, creating the possibility for extreme flooding. Hence, studying flooding and how to mitigate the extent of disasters is critical. Hydrology also encompasses water quality. This is important as poor water quality creates health issues. The degradation of water goes hand in hand with the development of a country (or surrounding countries). As a country becomes more developed, the water quality will decrease as industrialisation and other harmful environmental problems increases. Although, the study of hydrology has some major threats: terrorism, pandemics, wars, etc. Through the study of hydrology, we understand that the solution for water problems needs to be quantified and mitigated at a catchment scale and not a political one, e.g. a valley rather a whole county or postcode. The catchment (drainage basin/watershed) an area of land draining through a river gauging station Types of catchments There are two main types of catchments: experimental and national/state. Experimental catchments are often researched between 0.1-10km2. Whereas national or state agencies gauged catchments, often research is an area of interest. For example, Wales (20,716km2) has 161 nested gauged basins meaning they have >15 per 2000km2. On the other hand, Malaysia's Sabah State (73,371km2) has 40 nested/rated gauged basins, meaning they have 1 per 2000km2. Why study at the 'catchment scale'? It allows the forecasting of floods and allows decisions on how to mitigate them. As well as quantifying and solving river water quality problems.

What Basin hydrological characteristics do we need to know (to solve)?    how much rainfall? is it a climate-driven system?  How much evaporation?