Hydrology is the study of water and how it maneuvers itself around, through, over and into rocks and sand and soil. Ground water when mixed with soil usually turns into mud. I say usually because some soil is so nonporous that when mixed with water it becomes clay. But the ground water we are concerned about here is water that manages to seep out of the soil leaving the grit and sand and other particles of matter behind. Rain is only one part of this recycling effort. That is, it falls to earth and then is taken up again by the sun and the process begins again.
Raindrops form when the rain clouds become too saturated with water to hold them back. As new moisture is enters the already filled cloud an escape valve opens and droplets of water fall to earth. These rain drops while still being held by the cloud have the same shape as rain drops but are smaller. It's their heaviness plus the force of gravity that ejects them downward.
Rain drops do not fall to earth at the same speed. Drizzle is when the rain falls haphazardly and hardly at all. The drops are smaller and do not fall straight down as they do when they are heavy and the air is not forceful enough to blow the drops to earth slanted. A drizzle is a steady rain but rain without much force.
The distribution of rain is not equal over the earth's surface. The amount of rain has to do with climate and temperature and wind force and proximate distances to open sources of rain. It stands to reason there will be less rain over dry arid deserts that there will be over areas that are dotted with lakes. In order for rain to fall on a geographical area there must be rain soaked clouds. For this there need be a continuous supply of water being taken up.
In other words, for an area such as a dry area without adequate water sources to receive rain, it most likely must blow in from other areas and produce rain clouds. The force behind this incoming rain must be forceful enough to change the everyday climate patterns for such and such an area. It all depends on how and where the wind blows.
About 70% of the earth's surface is covered with water; yet not all that is fresh and is usable by people and animals. In order to make some of the unusable portion of this water useful, it must undergo changes. Sea water is usable when the salt has been extracted, muddy water eventually filters itself of its contaminants, and contaminated water is treated by several different methods to render it usable.
This article is about raindrops that are formed from ground water or the water that is taken up by the sun. It is about water that escaped the mud pie stage and has flowed through sand and gravel and has, for all intents and purposes, recycled itself. Somehow, there is a separation, or some kind of demarcation line between the ground and the water. The solid matter settles to the bottom and the water devoid of its substance stays on the top.
This is by no means a simple procedure, nor is it a static one. Water is constantly moving. It is filtering itself downward or is being forced upward. Artesian wells are those wells that are formed when a hot water bed underneath the earth's crust finds a crack or an opening and rushes through. These wells are natural or are artificially made. When made by man and machine, the rock is drilled through and the pressure is released and is forced upward where it is formed into a well.
Other types of artificial wells are surface wells and are often referred to as dug wells. That description means workers manually dig down until they find water. There may not be any water close to the surface since some underground water is miles and miles down.
Water naturally flows downward toward the point of least resistance, unless of course it is being heated by underground agitation causing it to rise to the surface. Artesian springs are naturally formed by this process.
This is one way springs are formed; another is by having some impenetrable layer such as limestone or sandstone blocking it from going farther underground and it stands on the surface. If it is stagnant, meaning it has no way out and is trapped water, it is not a good source of water for human consumption.
The best springs are those that contain pools of runoff water that has outlets and and are continually refreshing themselves. The only way stagnant water gets refreshed is by being taken up by the sun into the atmosphere and then rearranging itself by the process of precipitation. One way of looking at rain is thinking that Mother Nature is doing her laundry. (Or, maybe just washing diapers) When the raindrops get too heavy they break through the flimsy net of mist and come back to the earth as rain. Most of the rain finds its way into the groundwater and the filtering cycle starts all over again.