Bringing it All Together

This work discusses the continuous movement of water on, above and below the surface of the earth. Brought into focus are the processes of the hydrologic cycle. This study is a useful starting point on the study of hydrology. The cycle begins with the evaporation of water from the ocean due to the heating of the water by the sun's radiation, thereby making it to change to water vapour and driven by air current in the atmosphere to form clouds which later condenses as rain. Processes of hydrological cycle takes place simultaneously at different rates and time. A concise history of the hydrologic cycle was also captured. Evaporation is seen as the major player in the hydrologic cycle.

Introduction: Water can occur in three physical phases: solid, liquid, and gas and is found in nature in all these phases in large quantities. Depending upon the environment of the place of occurrence, water can quickly change its phase. The hydrological cycle is a model used to describe the different stages water goes through during its journey from the oceans to the atmosphere, onto the land and back to the oceans. According to National Research Council (NRC, 1982), " The hydrological cycle is the pathway of water as it moves in its various phases to the atmosphere, to the earth, over and through the land, to the ocean and back to the atmosphere".

Water Encyclopedia, 2005

The hydrologic cycle is the endless circulation of water between the earth, the oceans, and the atmosphere, and is fundamental to the study of the waters of the earth. The cycle entails a huge turnover of water and is driven by the energy of sun and gravity. It has profound influence upon the landscape and earth's climate. The major components of the hydrologic cycle are precipitation, evapotranspiration, interception, infiltration, overland and channel flow, and ground water flow. Quantitatively, the hydrologic cycle is represented by a mass balance or continuity equation. The relative significance of the terms of this equation depends upon the space and time scale. Human activities and the hydrologic cycle are interactive and influence the earth's climate.

This describe the The Hydrologic Cycle

Surveys in Geophysics, 2014

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2005

A catchment is a basic unit of landscape particularly for investigations of hydrologic processes. Typically, the topographic boundary of a catchment coincides with the hydrologic boundary causing any precipitation falling on to the catchment to be routed to a stream where it is transported out of the catchment. Fundamental components of the hydrologic cycle, such as precipitation, runoff and evapotranspiration (computed by difference between precipitation and runoff over long periods), have been documented from water balance studies on small catchments. Observations and time series data collected from small catchments provide a basis for the development of hydrologic models, and many such models have been used for flood forecasting. However, one of the more recent goals of hydrologic investigations in small catchments is to understand better how streamflow is generated and how this process relates to water quality genesis. Prior to the last few decades, studies of the sources of str...

JOURNAL OF JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2016

In this article some fundamental issues in hydrologic modeling are discussed, and some emerging methods toward their solutions are presented. INTRODUCTION Many of the hydrologic modeling tools date back to 1960's, such as Sugawara's tank model, and, later, the Stanford watershed model, which formed the basis for the conceptual watershed hydrology models that have been used by government agencies and practitioners all around the world. These models are still being in current use as the main tools for hydrologic water balance studies, environmental modeling studies, flood forecasting, seasonal flow forecasting, etc. Meanwhile, for the risk-based analysis and design of hydraulic structures the standard methods have been the flood frequency analysis and the probable maximum flood estimation. The flood frequency analysis procedure was standardized in the USA in mid-1970s by the development of the Bulletin 17 by the US Water Resources Council (1976). This standardized flood frequency analysis method was revised in 1982 by the US Department of Interior Interagency Advisory Committee on Water Data (1982), and has been used for more than 30 years until present by all US Agencies and water resources engineering practitioners in the US and elsewhere around the world. As for the design of very large hydraulic structures and nuclear power plants, the probable maximum precipitation procedure was developed by the US Weather Bureau in mid-1950s (US Weather Bureau, 1956). While it has gone through some minor revisions through a series of Hydrometerological Reports, this approach to the estimation of probable maximum precipitation was adopted by World Meteorological Organization (WMO, 1986), and have been practiced around the world. The probable maximum flood has been estimated by rainfall-runoff models that used various-duration probable maximum precipitation estimates as their input. With the emergence of climate change as a major issue for the earth system, many standard methods in hydrologic modeling that are based on the fundamental assumption of statistical equilibrium of the hydro-climate of a study region, are now in question for their scientific basis. Furthermore, sparseness or lack of atmospheric and/or hydrologic data at many regions of the world have prevented rigorous hydrologic modeling efforts for the assessment of water balances and