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In terminology, hydrological originally comes from the Greek “hydro” which means water and “logos” means science. So, from its original words, hydrological is the science of water. In engineering geography, hydrological is one field that deals with all elements in the process of recording, surveying, and mapping the state of water on earth’s surface. Thus, the hydrological field is closely related to climatology, meteorology, and geology because hydrological is a system that’s interrelated with the movement of the earth’s crust, the quality and water resources contained in the surface of the earth. This system is also called the hirdology system, and there are 3 types of hydrological cycle. 

The hidrological or water cycle is a cycle of the formation of rain or snow, which becomes water and returns to its original source throughout the year. This can be explained as follows. When seawater and river water on the ground surface evaporates due to sun exposure, the water evaporates and becomes water vapor in the process of atmosphere circulation. After that, the water vapor experiences condensation to form clouds that contain water drops, and subsequently experiences heating until finally the rain or snow finally fall down. When the water falls into rain and snow to earth, the water is blocked by existing trees and vegetation, causing runoff on the surface land and re-enters the soil or replenishes water discharge into oceans and rivers. Furthermore, water from the river flows back into the ocean, and repeats again. This cycle repeats continuously throughout the year.

Based on the understanding, the hydrological cycle has a very broad scope because this cycle covers the origin and process of the water movement occurrence and its distribution, as well as the properties and relation of water to the original environment and life on the earth’s surface. Therefore, the hydrologic cycle explains the continuous cycle of water. So, the kinds of hydrological cycles are based on the process of forming water on the earth’s surface, including the following:

• Evapotranspiration

This process is a combination of evaporation and transpiration processes. Evaporation is the process of evaporation from oceans, lakes, and other water masses that are above the surface of the land or earth. While transpiration is the process of evaporation of water from plants.

• Evaporation

The process of transforming water molecules into steam which requires the help of heat radiation energy from direct sunlight. At the time of changing this water molecule there is a force from the surface where the evaporation takes place originating from the difference between the vapor pressure of the water on the evaporated surface and the pressure temperature that is around the evaporation site. During this evaporation process the air temperature around the evaporation site accumulates and becomes saturated, so the evaporation process becomes weak and can stop when the wet air is no longer transferred to the atmosphere.

• Transpiration

This is a evaporation process that occurs in plants. This is caused by a very saturated pressure between the wall of plants’ cell with a layer of atmosphere located outside or around the plant. At the time of the evaporation, the transpiration process depends entirely on the energy supply from the sun’s radiation, humidity, temperature, water vapor pressure, and wind. While from within the plants themselves, the significant factors are the physiological factors of the plant and the surrounding environment, such as climate and soil conditions. The inspiration takes place throughout the day when it is directly under the sun’s rays and occurs in the stomata, the pores located under the leaves.

Also Read : 7 Utilizations of Water Resource in Human Life

From the explanation of the hydrological cycle along with the process of the above mentioned cycle, the next section explains 3 types of hydrological cycles that occur on the surface of the earth, among others as follows:

1. Short cycle
2. Medium cycle
3. Long cycle

Short cycle or often referred to as a small cycle is a hydrological cycle that occurs in the ocean. The cycle itself is very simple through three stages. First, the seawater undergoes a process of evaporation due to direct emission of sunlight and then it becomes a gas vapor containing water molecules. After the gas vapor goes into the atmosphere, water molecules condense and form clouds that contain water droplets. After condensation in the cloud layer becomes saturated due to direct sunlight, the cloud containing water molecules turns into rain and drops to the surface of the ocean. This process takes place throughout the year and only takes place in these ocean areas.

In the medium cycle, the process occurs in two places : rivers / lakes / reservoirs and seas. This process is related to one another. This can be explained as follows: when water in rivers / lakes / reservoirs and the seas experience evaporation and becomes a gas vapor containing water molecules due to direct exposure to direct sunlight radiation, water from both places undergoes an evaporation process. Then, the gas vapor containing the water molecule goes up to the atmosphere and forms a rain cloud. The influence of wind gusts causes the rain clouds to move inland due to saturated condensation, causing the rain clouds to fall into rainwater on the surface of the land. When the rain water fills a river or lake or reservoir, the water is channeled back to the ocean.

The last cycle of 3 types of hydrological cycle is a long cycle or also called a large cycle. This process occurs in areas that have temperatures below zero degrees Celsius or cold temperatures. The process can be explained as follows: when seawater experiences evaporation and becomes a gas vapor containing water molecules due to direct sunlight, the gas vapor is sublimated. After that, the formation of clouds containing ice crystals while in the atmosphere. Then, the cloud containing the ice crystals moves to the mainland because of a very strong gust of wind and then falls to the snow due to continuous sunlight and wind factors. When the snow falls on land, the snow forms glaciers. Due to direct sunlight throughout the day, the glaciers melt and form a river flow. Thus, water from melting glaciers flows in the flow of formed rivers which eventually empties back into the ocean (also read : 4 Differences in Seawater and Mountain Water).