Building greenhouses for vegetable and plant growing system is a sustainable way of harvesting rainwater. A transparent wall and roof structure made primarily of materials such as glass, used to grow plants that require controlled climatic conditions. Crops are exposed to the optimal amount of sunlight for the warmth they need and protection from excessive heat and cold. Modern greenhouses are equipped with shielding facilities, heating, cooling, lighting and computers to provide optimal conditions for plant growth and microclimate control. Water is a precious resource that plants need to grow. We tend to take our water supply for granted until its quantity and quality decline. As in any agriculture, irrigation is also a key requirement for greenhouses. Greenhouse crops may require up to 0.4 gallons of water per square foot of growing area per day. Of course, the amount depends on the type of crop, the season and the place of origin. Installing rainwater harvesting systems in combination with greenhouses can help meet the demand for greenhouses, especially in arid regions of the world where groundwater is scarce.
- Expected Harvest through greenhouse RWH systems
Estimated rainfall from a greenhouse rainwater harvesting system can be calculated with a simple calculation. Divide the total catchment area measured in square feet by 1,000 and multiply the result by 550. This determines the number of gallons of water that should be collected per inch of rainfall. Then multiply that result by the average annual rainfall in your area to get the amount of water you can collect. About 20% of water loss is due to evaporation, leaks, clogged drains, etc. On average, one inch of precipitation per acre in a greenhouse is 550 gallons per 1,000 square meters. This amount is enough to make a big difference. Types of Greenhouses The basic design of a greenhouse depends on many factors, such as the types of materials used, construction methods, equipment, and equipment. Therefore, there are multiple ways to classify the types of greenhouses. Some common ones are:
- Based on location
Colder regions such as Central and Northern Europe have glass greenhouses, while warmer Mediterranean regions cover greenhouses with plastic sheeting to provide additional protection from adverse environmental conditions. These areas have wide-span, plastic and vaulted Venlo type greenhouses.
- Based on the shape
The most common forms found in greenhouses are: gable or pitched roof sawtooth roof or pitched roof round arched tunnel circular arches with vertical sidewalls, lancet arch with sloping sidewalls, Lancet arch with vertical sidewalls.
- Based on the construction materials
Greenhouses can be made of wood, steel, aluminum, or a combination of both. Each has advantages and disadvantages. Glass, composite panels, hard plastics, and plastic films are commonly used for cladding. - Based on facilities and equipment Low Tech Greenhouse It uses simple technology with little to no automation. Low structures without vertical walls (may be less than 3 meters in total height) made of wood, bamboo sticks or steel. 
Ventilation is largely passive, and the internal climate is highly dependent on external conditions. This type supports low-yielding crops and requires careful management against pests and crop diseases. Medium Technology Greenhouse Using galvanized iron and aluminum in the structure, it has a more stable structure. The vertical walls are 2-4 meters high and the total height is less than 5.5 meters. They are covered with single or double plastic film or glass. They use varying degrees of automation for indoor climate control. High Tech Greenhouse These are modern and most complex structures, built with a galvanized iron support structure, an aluminum glass support structure and glass as the cladding material. The vertical walls are at least 4 meters high and the roof apex is up to 8 meters above the ground. Equipped with advanced computer technology and equipment to ensure optimal ventilation, temperature and incident light to provide a climate-controlled growing environment. Any type of greenhouse can be combined with a rainwater harvesting system. The greenhouse roof is employed as a guttered drainage surface, with a series of gutters connected by 4" or 6" PVC pipes. As the number of gutters increases, the downspouts connect to larger pipes (terminal pipes can be up to 18 inches or more in length for large greenhouses). Pipes should be installed with a minimum slope of 1/16 inch per foot and cleaned every 100 feet. The design uses a fast flush system and filtration technology with filters to limit debris and contaminants from entering pipes and storage equipment.
Storage tanks made of common materials (concrete, steel, wood, plastic) are used to collect the filtered water. For large greenhouses it is usually desirable to build a pond to hold the collected rainwater. Pond size is recommended by a licensed engineer after considering internal combustion engine system capacity and legal limits. If the soil is porous, line the bottom of the pond with a vinyl liner to prevent seepage. While this is a good option, the water collected in the pond will become contaminated with algae growth. Finally, the water from the storage is distributed to the greenhouse using a conventional irrigation system. Overflows are dealt with by diverting excess runoff into wetlands or drainage areas to keep your property and neighboring properties from being flooded. Advantages of using rainwater in greenhouses In addition to the usual benefits of rainwater harvesting, RWH systems in greenhouses have unique benefits such as: Rainwater is generally soft and contains few chemicals. It has a calming effect on crop quality. Gutter greenhouse designs can collect large amounts of water at a reasonably low cost. This reduces the stress of physically watering plants and promotes convenient irrigation. Clogged micro-irrigation pipes are a big problem. The chemical composition of rainwater can greatly help solve this problem. Reduces greenhouse operation and maintenance costs by saving labor, pesticides and electricity for pumping water. Rainwater harvesting in greenhouses is now a global phenomenon. He also receives support from many state governments to promote organic farming.