How to grow food and get fresh water in deserts near the sea

There are many places near seashores where there is very little rain. A lot of the shore region in the Middle East is classified as desert for this reason. These places are also found on the west coast of South America and southwestern part of North America. Let’s start with the fact that there is plenty of sunshine and salt water available. The water usually does not have much mineral nutrients in it but these can be easily and inexpensively added. Now consider constructing a string of connected shallow water channels with a black water proof lining. This should be done on level ground well above any possible flood level. But it should not be too high to easily pump sea water to it. If the local sea water is pumped into these channels and a small amount of fertilized is added, we will get a bloom of plankton. Now consider a continuous slow pumping of water into one end of these channels and emptying the other end into a large pool. Let’s say that the rate of pumping water into the channels is set so that The water spends several days in the channels before it enters the pool at the end. This water will have a high concentration of plankton. This is food that can be utilized in several ways. For example, the pool can be stocked with filter feeding fish. These can be harvested and eaten by humans. There are many other animals that live by filtering food from water. Probably the one that actually consumes the most plankton is krill. They, too, can be easily harvested from the water in the pool. It is also possible to use the plankton directly to prepare food for humans. Consider that the plankton is a mixture of plant and animal matter that is actually the base of the whole oceanic food chain. There is no reason that it cannot be added to other foods to increase their nutritional value. After removing the food in the pool, there will still be high levels of nutriments in it so that most of that water can be recycled back to the beginning of the water channels. There it will mix with the incoming sea water and support further growth of plankton.
But you remember that the title of this article also mentioned getting fresh water. Let’s go back to considering the water channels that are growing the plankton. Let’s say that they are about one meter wide and half a meter deep. With these dimensions, they can use common window glass that is often used for residences. They can be covered by clear glass, and the sunlight, assisted by the black lining on the bottom of the water channels will raise the temperature of the water because of the greenhouse effect. The warmer water will increase the rate of growth of the plankton and it will also increase the humidity of the air above the water. Some fresh water will then condense onto the bottom surface of the glass. If the glass panels are tilted so that the water will run down and drip off the bottom edges of the panels into small channels, that water can be collected and can be used for drinking water or irrigation. During the day, the water in the channels will get quite warm. Since water has a very high specific heat, it will store a lot of thermal energy. In desert areas, the air temperature drops quickly at night because there is little water vapor in the air to block heat radiation to space. It is common to have very large differences between day and night temperatures. At night, the glass panels will get cold and the rate of condensation will increase greatly. The evaporation of the warm water in the channels will cool the water. Therefore, the excess heat that was collected during the day will be used to distill fresh water from the salt water in the channels at night. One result of this distillation is that the concentration of salt in the water will increase and this highly salty water must be removed. After the water gets to the pool at the end of the channels, The food is utilized as described in the first paragraph. But then the salt level will be too high to recycle more than a small amount back into the channels along with the incoming salt water. Instead of discharging it back into the ocean, since it still contains useful nutrients, it can be used to create a bog on land where it will support further plant and animal life. Another use for this water would be to use it as a nutrient source for oyster beds in shallow coastal water. There would be more fresh water generated than the local residents would need. This could be used to grow large amounts of food in greenhouses for local consumption and external sale.
The energy necessary to run this system is very low, A good source would be solar electric panels used to run the sea water pumps that refill the channels. Another way of pumping the water is to use windmills. These do not need to generate electricity but can instead directly drive pumps that fill the channels with salt water. I have seen pumps constructed from old tires and scrap metal that were driven by windmills. This system is low tech and can be built and maintained by people without specialized training. Operating this system would provide livelihood for a community of people. They would provide their own food and could sell surplus food and fresh water to earn money. As the local population grows, the size of the plankton growing system can also grow. None of the materials used are consumed, except for a small amount of fertilizer, and all of the materials are inexpensive. There is labor needed to maintain the system, keep it clean and repair it when necessary. The land used will be cheap because it is otherwise unusable, so building a stable self sufficient community should be easily possible with very low start-up cost. There are thousands of suitable locations, because there are many deserts with ocean access. Just on the southern shores of the Mediterranean Sea, there could be nearly continuous strings of communities operating this way. Once these communities are functioning, there will be opportunities to develop other kinds of work for the people not directly working to maintain or build onto the basic system. This could lead to light manufacturing enterprises or many other activities.
Labels
Use of desert land, Growing food with sea water, desalinating sea water, growing and using plankton on desert land, solar distillation of sea water, small self sufficient communities. low tech industry