Surface water hydrology describes the relation between rainfall and runoff, which is important for water resources for drinking water, agriculture and the environment, and for protecting and safe-guarding people against possible floods. Surface Water Hydrology relates to the dynamics of flow in surface water systems (rivers, canals, streams, lakes, ponds, wetlands, marshes, arroyos, etc.). This includes the field measurement of flow and water levels, the relationships between these two variables, the statistical variability at each setting, and then development of the levels of risk. Examples include base flow needs for instream flow, drought susceptibility, and flood levels. In-depth analysis of surface water components of the hydrologic cycle: hydrometeorology , evaporation/transpiration, rainfall-runoff relationships, open-channel flow, flood hydrology, and statistical and probabilistic methods in hydrology.