Selecting a Site
Before you can determine where you will find water inside the ground, you need to understand how water gets into the ground and how it is stored there.
In the next three sections we will discuss the way that water is kept inside the earth and how it becomes safe to drink.
If you already know about the water inside the ground, you may want to jump to the last three sections of this chapter. These sections discuss features of the earth that you should be aware of when you choose your well site, the surface features to avoid around your well site, and how to choose a site that people will want and use.
The weather/water cycle
All the fresh water (water that is not salty) on the earth has come from the clouds in the form of rain.
How did the clouds get the water?
As the sun warms up the water on the earth, whether it is dew on grass, the lakes and rivers, or the oceans, it causes it to turn into steam. This is called evaporation.
You can see evaporation clearly in a pot of boiling water. The steam rising from the pot is evaporated water. If you hold something inside the steam it is soon covered with water because the evaporated water has the chance to collect and become visible drops of water again. The same thing happens to a lake, or the dew, or the ocean, when it is heated by the sun. Other forms of evaporation can be seen in the fog after a rain or in the mist around a lake.
All of this evaporated water rises up into the sky where it forms the clouds. When the clouds become full of evaporated water, then the steam collects to become drops of water which fall back to the earth.
But if the water evaporates from the salty oceans, why does it taste fresh when it rains?
Ocean water is just fresh water with salt and other things mixed in with it. When the water evaporates it leaves behind whatever was mixed with it. So the water leaves the ocean but the salt stays.
Try this experiment: take a handful of water and put it in a clean cooking pot. Mix in some salt or sugar until you can no longer see them. The water should now taste salty or sweet. Now boil the water over a fire or stove until all the water has disappeared (evaporated). There will be some dusty stuff left on the bottom of the pot. Taste the dust after it has cooled. It will be the salt or sugar that the water left behind.
So the drops of water that fall from the sky are fresh and we can drink them without having to worry about becoming sick. All of the things which can cause illness that mix with the water in the rivers or on the ground are left behind when the water becomes steam.
How water is stored in the ground
How does the water from the rain get inside the earth and how is it kept there? When we pour water onto soft dry soil or sand we can see that it will soak in quickly. Hard soil may soak in the water but not as quickly as soft soil. Clay will not soak in water. Rocks will not soak in water, either, but if the rock has cracks it can hold water inside the cracks.
Soil and sand can hold water because it has space or air inside it. If you take a piece of dry, soft soil in your hand and squeeze it, you can make it smaller as the grains of soil move closer together and make the air leave the soil.
Try this experiment. Fill a pot with dry soil or sand until it is full. One might think that since the pot is full, it cannot hold more. Now start adding handfuls of water. Count how many handfuls of water you can add to the pot. You may have to wait a few minutes or even an hour for the water to soak in, but keep adding water until the soil will not absorb any more. (Remember to keep the pot out of the sun so that the water will not evaporate!) This may take a whole day, but in the end you may be surprised at how many handfuls of water the soil can hold. Put an equal number of handfuls of water into an empty pot just to see how much water the pot of soil holds. Imagine how much water a pot the size of your village or town would hold if the pot was 100 feet deep! There are no such things as lakes or streams under the ground, there is only soil...and soil can store a lot of water!
This is how water is stored inside the earth.
But how does it get there?
When the rain falls on the earth some of it gets soaked in by the soft soil. (This is called absorption.) Much of the rain runs across the surface of the land and goes into the streams. And some of the rain evaporates again.
The streams carry the water to lakes or oceans where it will evaporate once again and repeat the weather/water cycle. But before the water in the streams reaches its destination some of it may soak into the soft soil or sand at the bottom of the stream.
What happens to the water that gets soaked into the ground? It cannot evaporate because the sun cannot warm it inside the earth. Instead it sinks because it is heavy. Water can move through the smallest pathway and can squeeze through the earths tiniest holes.
Try this experiment with a group of friends. Have everybody cup their hands to hold water. Pour a equal amount of water into each persons cupped hands and then see who can hold on to the water the longest. Some might be able to hold on to the water for a few minutes, but as soon as the water finds a hole, no matter how small, it will move through it.
Another thing that happens to water when it sinks inside the earth is that it sticks to things. When we swim in lakes or rivers we are surrounded by water. When we get out of the water most of it falls back into the river or lake because it is heavy. But a little of the water sticks to us. We can watch the water slide down our body because of its weight. We can see how smaller drops of water join together to make bigger drops of water. The bigger drops of water become too heavy to stick to the skin and fall off.
Water will stick to things but it does not stick well enough to hold much weight. Like a man who can hold onto a tree branch with one hand and hang in the air. He can only hold himself, but if he were carrying the weight of three other men, he would fall to the ground. Water can stick to things if it is very small and does not weigh much.
You can see water sticking when you hang wet clothes out to dry. First the water will sink to the bottom of the clothes and gather to make drops which fall off the clothes. After awhile the tops of the clothes are dry but the bottoms are still wet and there is not enough water to form drops. The small amount of water sticks to the clothes and we depend on the sun to cause the water to evaporate.
Inside the earth you can find water sticking to things. When you dig a hole in the ground, is the surface dry and hot but the soil at the bottom of the hole damp and cool? This is because some water stuck to the soil as it passed through after the last rain.
Try this experiment. Take a tin can, gourd, or other container that will hold water. Make some holes in the bottom with a nail. Line the bottom on the inside of the container with a piece of scrap cloth to act as a filter to prevent things from falling out. Then fill the container with dry soil. Hold the container of soil over a clean pot and very slowly pour a cup full of water over all of the top of the soil. Wait and see if the water pours out the bottom of the container. Note how long it takes for the water to drip out. When the water has stopped dripping, pour the water caught by the pot back into the cup. Is the cup full? What happened to the rest of the water? It is stuck to the soil inside the container! Did you see how long it took the water to pass through? Water will pass through sand much faster than soil. Try different types of soils and see which ones the water moves though the fastest. The water is slowed down because it sticks to the soil as it passes.
Inside the earth the water may only be able to move a few inches each day as it squeezes through the tight soils, but its weight will keep it moving.
If the earth was made of only soil, the water would sink forever, but the earth has many rocks, much clay, and even very hard soils that will not allow water to pass. So the water sinks until it runs into clay or rock or hard soil that it cannot pass through.
If we look at the earth where it has been cut by rivers we can see in the sides of the cut that the earth is made up of many layers of different types of soil, clay, sand, and rock. So where the surface of the earth may be soft soil, it may have sand beneath the soil and clay beneath the sand and rock beneath the clay and more clay under the rock and so on...
Since we cannot always see with our eyes what is under the ground, we will make drawings which demonstrate what the earth would look like if it were sliced open. If there are river canyons, rock quarries, mines, or gravel pits near where you live, you may be able to see there the evidence of layered earth.
If water has been sinking in soil and sands and then runs into a layer of clay or rock, two things might happen: 1.) The water may just stop sinking and collect there on top of the clay or rock, filling in all the spaces between the soil or sand, or 2.) the water might move sideways along the top of the clay or rock. Water under the ground will act just like water on the surface. It will always try to have a level surface, like that of a lake. It will fill up an area and then flow over the top, like a bowl of water overflows. It will keep moving until it has poured into a river or an ocean or it has been trapped. Remember, however, that the groundwater may only be able to move an inch a day. Still, it will keep moving until it is level.
Those places where water has filled all the spaces in the soil, or the cracks in the rocks, and has collected to create an area soaked with water is called an aquifer. Aqua is the Latin word for water. Sometimes there is more than one aquifer. You may drill and find an aquifer on top of a layer or clay, but if you drill through the clay you might find another aquifer underneath on top of a deeper layer of rock. When we drill for water in the earth, we are looking to drill into an aquifer so that we can remove the water.
Why the water in the ground is clean
As we said before, all the water in the aquifer comes from rain. The rain comes from evaporated water and has lost all the things mixed up in it, including those things that make people sick, like bacteria, worms, and other parasites. We can drink rain water without getting ill because it is clean. But as soon as the water touches the earth or goes into the river it mixes with whatever may be on the land or in the water and becomes dangerous to drink again.
The water in the aquifer has come from the stream or the surface, where it could easily have gotten mixed with human and animal waste or with parasites that could be harmful. So why do we think that the water inside the earth is clean and safe to drink?
There are two reasons that the water in the aquifer is considered to be clean. The first reason is that some of the parasites that spoil the surface water cannot live without light and air and so they die when they go inside the earth. But the most important reason is that the earth acts like a filter.
A filter is a device that will let one thing pass through it but not another. Mosquito mesh is a kind of filter that will let air and wind pass through it, but not mosquitoes and flies. A fishing net will allow water to pass through it but will filter out the fish. When we pour oil or other liquids through a cloth to strain out the impurities, we are using the cloth as a filter. Even a piece of glass can be a filter: it will let light pass through but not the wind.
When the water from the surface of the earth moves through the soil, it gets filtered by the soil. The soil that the water moves through may have holes so small that we cannot see them with our eyes, but we know water can move through them. When the water passes through the soil it loses the impurities mixed with it.
Try this experiment. Find the person who was able to hold the water in his or her cupped hands the longest in the earlier experiment. Mix up a handful of soil with a cupful of water and pour it into the cupped hands of this person. Catch the water as it drips from the cupped hands and note how much of the dirt made it through the hands and how much was caught behind in the hands.
This is an example of how the earth filters water. Of course, in the earth there are even smaller "filter" holes and the water can become much cleaner. The water passes through the soil and the germs and parasites that can make us sick are left behind.
The earth cannot filter minerals, like salt, which is why some drillers near the ocean find undrinkable salty water in their wells. But while most other minerals may make the water taste differently, they are not usually dangerous. The only danger in this regard is if the well you want to drill is near a factory or gasoline station where chemicals are spilled or dumped into the earth. These chemicals cannot be filtered and can poison a well. This is a big problem in many modern countries where aquifers that were once perfectly safe for drinking have had to be abandoned because of chemical pollution.
In general, water is considered to be safe for drinking if it has passed through 30 feet of earth. Of course, this is only a rough figure. The type of earth is important. If the soil is packed close together, then the holes will be smaller and they will filter out the things that make people sick after the water has passed through only a few feet. If the soil is loosely packed, like sand, then water can move through it more quickly and carry the contamination further.
We will talk about this more when we talk about finishing a well, because if the well hole is not sealed up right after the hole has been dug, then impurities can race down the side of the new well without being filtered by the soil. This would spoil the aquifer.
If you are worried that your aquifer might be spoiled, you can follow the steps for disinfecting the well that are listed in chapter eight. Most governments and health departments have someone who will take a sample of your well water to a laboratory and test it for spoilage and minerals.
Geological features to be aware of
There are many things to look for when selecting a well site. The best clue to where water may be is experience. Other well drillers or diggers may know where water can be found in your area. If you keep good records every time you drill, which we will discuss later, you will soon learn what to look for in your area.
There is no sure way to find water. The most modern driller with the most expensive tools still cannot know where water is. You should expect that you will drill many dry holes in your drilling career.
Still, knowing where to start looking is important and will help you to find water faster than just guessing. Here is a small list of things to look for in the shape of the earth and the types of soils and plants.
Lakes, swamps, and rivers
Lakes, swamps, and rivers often indicate the top of an aquifer.
Lakes, swamps, and rivers are usually found at the lowest point in a valley. The water that fills the lake or river is part of an aquifer, it just happens to be exposed.
If you drill into the earth alongside a lake or you can expect to hit water at the lake level. That is to say, if you were on dry land four feet higher than the level of the lake and were to drill down five feet into the earth, the bottom foot of your hole would be filled with water. It would match the level of the lake because, whether under the ground or on the surface, the water always tries to keeps a level surface.
When the water is moving through the earth and hits a layer of clay or rock that it cannot pass, it may move along the surface of the clay or rock. If the clay or rock sticks out of the side of a hill, then the water will pour off of the clay or rock. When we see this it looks like the water is coming out of the earth. This is how natural springs are made. Water that comes from springs is rain water that has sunk from the surface to the top of the clay or rock. This is why springs are only found in areas with hills and mountains.
Many springs can be converted into springboxes which will provide plenty of clean, filtered water. If you have a spring you may not need to drill a well. But if the spring is not in a good location or if the spring does not provide enough water, then knowing where the spring is may give you some clues where there might be water under the ground in other locations.
When you are looking for a place to drill, pay attention to if and where rocks appear around your area. If there are large rock walls around the area, in the valleys or lower areas, look at the rock. Is it one large piece or does it have layers? Strike it with a hammer. Does it break easily? Does it crumble? A rock with layers, that breaks easily or crumbles when hit by a hammer is a rock that you can drill through easily. Rocks that are solid and that will not chip easily when struck may be difficult to drill through.
Are there stones larger than two feet thick lying about the area with few other rocks nearby? Are they hard to chip? You might run into one of these stones, which are also called boulders, while you are drilling. By trying to chip the boulders on the surface and seeing how easily they break, you can determine whether or not you want to try to drill through them if you find one when you are drilling the well. If there are such boulders around your area, note their size. You can expect that the boulders inside the earth would be the same size. If there are boulders in your area, and your drill meets up with one, you can sometimes move the drill a few feet in either direction and drill past the boulder.
Are there many smaller stones in the area? Will they break easily when you strike them? Would they fit inside the drills bailer?
By looking at all the stones on the surface and breaking them up, you can get an idea of what you will find when you drill. Pay close attention to how the fresh rock chips look. When you are drilling you will be able to compare the chips that you bring out of the hole with the bailer and know what kind of rock you are drilling into.
If there are many large rocks in one area, you will probably want to drill in other areas where there are not so many rocks. Rocks can be drilled, and in many cases rocks with cracks full of water make great aquifers, but they are harder to drill.
Places where plants look green and healthy through the dry seasons usually have water in the ground that keeps the plants healthy. Look for large trees that usually grow around water like streams and lakes. These trees require much water to survive and if the source of the trees water is not easy to find on the surface, it may be an aquifer under the ground.
Hill and Valleys
Water will always move downhill. The lakes, streams, and swamps where the water collects are always at the bottom of hills. There may be an aquifer above the level of the local stream or lake, but this is rare for shallow wells.
In Liberia we ran into a situation where the Chief wanted the well next to his house, which was on top of the tallest hill in the village. We suspected that the aquifer was about 40 feet beneath the village, but the chiefs house was another 40 feet above the village. This meant that we would have to drill twice as far to reach the aquifer.
We did drill next to the Chiefs house, but we ran into rock within 20 feet.
You may usually assume that steep hills are made of rock. Loose soil is usually washed down from the hills into the valleys, leaving behind the harder soils and rock.
The collection of soil in the valley bottom means that there will be plenty of room for water to be stored in aquifers. Some of the best places to drill are along the sides of valleys where the well will be high enough to avoid flooding but can reach to the bottom of the valley where the water is stored.
Surface features to avoid
Besides avoiding rocks and the tops of hills, what else should the driller look to avoid in choosing a well site?
To avoid spoilage, the well should be located far away, at least 200 feet, from graveyards, latrines, baths, sewers, and places where animals are penned or wastes are dumped.
Ask those who live in the area if the place where you want to drill a well ever floods. Some land looks dry and fine most of the year but may become flooded during the years heaviest rains. A well in an area that floods, if even for a day, will be spoiled and dangerous. Look for a place which is high and dry all the year.
The site will be more comfortable with shade from small trees, but larger trees with powerful roots could damage the well in later years.
It will be important to keep animals away so that their wastes will not spoil the well. So the well should not be located in an area or on a path often used by animals unless a fence can be built around the well to protect it.
There are many things to think about when trying to decide where the well should be drilled. After looking at the earth, the soils, and the shape of the land, one must consider other, more human needs.
There are many things to consider, some will be more important to some people than others. Sometimes things that seem to be important need to be ignored so that the wells users will be happy. Unless the quality of the wells water is threatened, the users needs should be placed first. After all, a well is only a success if the people use it.
Women, especially, should help decide where the well should be. In most places the women take care of the water for the family. They are the ones who will use the well more and will make the well a success. Although the women may not usually take a part in such decisions, it is important for them to do so when deciding the well site.
Everybody will agree that it is nice to have the pump near their home, but it is very important to have the pump equally available to everyone who will be using it. A pump very near one home may not seem easy to use by those who live in other homes, especially if there is a dispute between the homes. On the other hand, those who live in the home next to the pump may be bothered by the noise and lack of privacy due to the others using the well.
A well in the center of the village may seem good, but may not be best if the center of the village is on a hill, or if there are too many rocks, or if the well will not allow the village to use the area for other things like important ceremonies, or if the animals spend their nights in the village center. In one case it was found that the village women avoided using the well in the middle of the village because they could not meet and talk in private at the well like they could at the stream.
In any case it is important that the well is located in a cleared area for safety. In one Liberian village, it was important to the residents that the well was in plain view of the adults so that they could watch to see if the children were treating the pump properly.
In another area, the village was having a dispute with the neighboring village. One way that one village would use "magic" on another was to place poisons in the water supply so that people in the rival village would get sick. The villagers in this area wanted the pump to be placed away from a path used by both villages and in a cleared area so they could see if a rival tried to spoil the well.
Local beliefs are very important. If there are places around the village that are taboo or haunted, they will make very unpopular well sites.
If the well site also doubles as the village football field or a parking place for cars, the well could be easily damaged in an accident.
Look for a site that is a clear improvement over the local stream or water hole. If the well is just as far from the village as the stream, then people can easily decide to get water from the stream if the well is being used by others.
Deciding where to put the well is the most important act. The best way to determine the site is to talk about it with everybody. Talk about the things listed in this chapter with those who will be using the well, so they have things to think about. And then listen. Listen some more. It may seem like a small problem to you, but if the people who are using the well have a problem with the well location today, it may become a very big problem in the future.One good thing about letting the users decide where the well should be drilled is that the driller will not be held responsible if the well does not provide water!