Hydrology is the scientific study of water: its properties, its influences, and its distribution over and under the earth’s surface. The branches of Hydrology include: Hydrogeology, Chemical hydrology, Ecohydrology, Hydroinformatics, Isotope hydrology, Surface hydrology, Hydrometeorology, Drainage basin management and Water quality. Surface Hydrology or Surface-water hydrology is a branch of Hydrology. It is a field that encompasses all surface waters of the globe (overland flows, rivers, lakes, wetlands, estuaries, oceans, etc.). This is a subset of the hydrologic cycle that does not include atmospheric, and ground waters. The study of surface water hydrology is vital because the quality of runoff water can affect drinking water sources and the relationship between rainfall and runoff can help predict and prevent the occurrence of floods. In general Surface hydrology is the analysis of surface-water components of the hydrologic cycle: hydrometeorology, evaporation/transpiration, rainfall-runoff relationships, open-channel flow, flood hydrology, fluid mechanics, and statistical and probabilistic methods in hydrology. Surface-water hydrology relates the dynamics of flow in surface-water systems. Surface-water hydrology relates the dynamics of flow in surface-water systems. Surface-water hydrology includes the relation between rainfall and surface runoff; this relationship is an important aspect of water resources for sewerage (wastewater) or (sewage), drinking water, agriculture (irrigation) environmental protection, and for flood control. Surface water hydrology is one of the key driving variables in river ecosystems. The relationships between groundwater and surface water includes baseflow needs for instream flow, and subsurface water levels in wells.