Civilisation depends on water and man has always been vulnerable to the problems associated with too little or too much rainfall. In adjusting to the natural vagaries of the climate, the impact of rising water demand and the effects of man-induced global warming, water management has become a very complex challenge. In meeting this challenge, hydrometric data (primarily river flow data but also rainfall and groundwater measurements) provide the key to understanding hydrological processes and are the essential foundation upon which improved river and water management strategies can be developed.
River flows are the combined result of the many climatological and geographical factors which interact within a drainage basin. This integration implies that river flows are the most directly appropriate component in the hydrological cycle for a wide range of applications. These include the assessment and management of water resources (including irrigation provision), the design of water-related structures (reservoirs, bridges, flood banks, urban drainage schemes, sewage treatment works, etc.) and flood warning and alleviation schemes. In addition, hydrometric data are essential for assessing and developing hydro-power potential and enhancing both the ecological health of water courses and wetlands and their amenity and recreational value.
In a digested form, river flow data underpin water policy initiatives and the drafting of protocols and legislation – for both national and international application. They also serve an important educational role contributing to a greater public understanding of water and water management issues.
As with many environmental datasets, river flow data assume a particular importance at a time of actual, or anticipated, change. With global warming expected to impact very unevenly on river flow patterns, in both spatial and temporal terms, observational records are the key to identifying, quantifying and interpreting hydrological trends. This is a necessary precursor to the development of more effective coping mechanisms in future flood and drought episodes.