On this page:-
- The water crisis
- Israel uses desal and recycling more than most countries
- Tal-Ya dew and water box
- Israel uses drip irrigation
- Experiments with seawater greenhouses
The water crisis
As the wiki says, “The most common threat to water security is water scarcity. There can be several causes to water scarcity including low rainfall, climate change, high population density, and overallocation of a water source. An example of periodic water scarcity in the United States is droughts in California. Another category of threats to water security is environmental threats. These include contaminates such as biohazards (biological substances that can harm humans), climate change and natural disasters. Contaminants can enter a water source naturally through flooding. Contaminants can also be a problem if a population switches their water supply from surface water to groundwater. Natural disasters such as hurricanes, earthquakes, and wildfires can damage man-made structures such as dams and fill waterways with debris.”
- America probably experienced ‘peak water’ in the 1970’s (Arstechnica).
- More than 1.2 billion people lack access to clean drinking water (UN).
- More recently, a majority of the world’s important groundwater reserves known as ‘fossil water’ have been overused and recent drought and local climate changes have depleted them further. Many are backup water sources for when the rains fail, only now these are failing as well. US Intelligence reports indicate this could cause conflicts and failed states (Guardian 2014).
Israel uses desal and recycling more than most countries
Israel have also built more desalination plants per capita than any other country on earth. Over half their population get their drinking water from desalination plants. Israel built 5 plants in the last 10 years to achieve this. While energy intensive, it only accounts for 3% of Israel’s annual electricity use to get 50% of their drinking water from the Mediterranean ocean. They have gone from water poor to water wealthy, and could soon be exporting water.
Israel are the world’s largest recycler of grey and black water for agricultural use, with local rural townships supply cleaned up waste water for local agricultural products in what would otherwise be desert. Their drip irrigation method saves 40% of the water usually used, and yet gets 50% better crop yields.
Qualification: Israel’s strategy appears to rely on high density populated townships in the deserts to efficiently recycle their grey and blackwater, focussing that cleaned up water into local agricultural projects as appropriate. I doubt this strategy would work over much larger areas, like moving waste water from Africa’s cities to the Sahara (a long distance indeed) or from China’s cities all the way up to China’s growing Gobi desert. Other more energy efficient, local and natural strategies are required for such vast areas.
The video above also mentions farming fish from salty underground desert water, and then feeding that salty, fish-waste water to salt-tolerant plants that love all the extra waste nutrients.
Tal-Ya dew and water box
Then there’s the Tal-Ya water box, a dew-catching tray that pulls the dew directly out of the air and funnels it to the plant. It can be used alone in some areas, or for dryer locations be used in conjunction with drip irrigation as well for maximum efficiency.
The Dutch also invented something similar with the Groasis Waterboxx designed specifically to establish trees in areas undergoing desertification. It collects dew and infrequent rain, and slowly releases it to the plants roots, promoting deeper root growth.
Israel uses Drip Irrigation
The wiki has an interesting list of advantages and disadvantages. One that strikes me is the sheer economics of setting up drip irrigation must mean that in a desert country, paying for plastic piping infrastructure must be cheaper than paying for the extra water a cheap giant surface farm sprinkler could distribute.
Advantages and disadvantages
The advantages of drip irrigation are:
- Fertilizer and nutrient loss is minimized due to localized application and reduced leaching.
- Water application efficiency is high if managed correctly.
- Field levelling is not necessary.
- Fields with irregular shapes are easily accommodated.
- Recycled non-potable water can be safely used.
- Moisture within the root zone can be maintained at field capacity.
- Soil type plays less important role in frequency of irrigation.
- Soil erosion is lessened.
- Weed growth is lessened.
- Water distribution is highly uniform, controlled by output of each nozzle.
- Labour cost is less than other irrigation methods.
- Variation in supply can be regulated by regulating the valves and drippers.
- Fertigation can easily be included with minimal waste of fertilizers.
- Foliage remains dry, reducing the risk of disease.
- Usually operated at lower pressure than other types of pressurised irrigation, reducing energy costs.
The disadvantages of drip irrigation are:
- Initial cost can be more than overhead systems.
- The sun can affect the tubes used for drip irrigation, shortening their usable life. (This article does not include a discussion of the effects of degrading plastic on the soil content and subsequent effect on food crops. With many types of plastic, when the sun degrades the plastic, causing it to become brittle, the estrogenic chemicals (that is, chemicals replicating female hormones) which would cause the plastic to retain flexibility have been released into the surrounding environment.)
- If the water is not properly filtered and the equipment not properly maintained, it can result in clogging or bioclogging.
- For subsurface drip the irrigator cannot see the water that is applied. This may lead to the farmer either applying too much water (low efficiency) or an insufficient amount of water, this is particularly common for those with less experience with drip irrigation.
- Drip irrigation might be unsatisfactory if herbicides or top dressed fertilizers need sprinkler irrigation for activation.
- Drip tape causes extra cleanup costs after harvest. Users need to plan for drip tape winding, disposal, recycling or reuse.
- Waste of water, time and harvest, if not installed properly. These systems require careful study of all the relevant factors like land topography, soil, water, crop and agro-climatic conditions, and suitability of drip irrigation system and its components.
- In lighter soils subsurface drip may be unable to wet the soil surface for germination. Requires careful consideration of the installation depth.
- Most drip systems are designed for high efficiency, meaning little or no leaching fraction. Without sufficient leaching, salts applied with the irrigation water may build up in the root zone, usually at the edge of the wetting pattern. On the other hand, drip irrigation avoids the high capillary potential of traditional surface-applied irrigation, which can draw salt deposits up from deposits below.
- The PVC pipes often suffer from rodent damage, requiring replacement of the entire tube and increasing expenses.
- Drip irrigation systems cannot be used for damage control by night frosts (like in the case of sprinkler irrigation systems)
Seawater greenhouses to green the desert
Anywhere you have desert next to the oceans, you can turn seawater into food and freshwater and a local green oasis. But this is such a big topic I devoted a whole RULE to it, see 8. REGREEN DESERTS.