Many urban homes in Kampala have ample compounds that are often unused and filled with paving stones or ornamental plants. However, these spaces can be transformed into productive areas for growing food crops like vegetables or fruit trees. By doing so, urban dwellers can produce their own food, save money, and promote healthy eating. However, one of the key challenges facing urban farmers is irrigation. To keep plants healthy and productive, they require large volumes of water – typically 2 to 5 liters per day per plant. This can be expensive for urban dwellers who often rely on piped water or rainwater harvesting. In this article, we explore the benefits of urban irrigation and provide simple techniques for using water more cost-effectively to support crop production in urban homes. This article equips the urban homeowner with practical strategies for harnessing the power of water to grow healthy, nutritious crops, regardless of the size of your compound.
Water Sources for Urban Irrigation:
There are several water sources that urban dwellers can use for irrigation. Buying water from the National Water and Sewerage Corporation is a popular option but it can be expensive. Rainwater harvesting is another option in Kampala. However is not always reliable, especially during the dry season. Rooftops are the most common surfaces for collecting rainwater, but any hard, impermeable surface such as driveways, walkways or patios can be used as well. Rainwater can be collected in tanks, barrels or cisterns, which can be located above or below the ground surface. The size of tanks depends mostly on the amount of water needed for irrigation and at times the amount of rainfall received.
A basic rainwater harvesting system includes gutters, downspouts, and a debris filter to remove leaves and other debris from the water. The filtered water is then stored in the tank until it is ready for use. While rainwater harvesting can be a reliable source of water, it may not provide enough water during extended periods of drought or very low rainfall. What if we recycle wastewater from our sinks? Household grey- water, which is generated from washing dishes, laundry, and bathing, can be cleaned and used for irrigation. The basic treatment process can include filtration and disinfection. During filtration, greywater is separated from solid particles like hair and other debris. A simple filter system made of sand, gravel, and a screen mesh can be used for this purpose. During disinfection, the greywater is treated with a disinfectant such as chlorine, hydrogen peroxide, or ultraviolet light to kill any harmful bacteria or viruses. After disinfection, the greywater is stored in a container until it is ready for use. The tank should be sealed to prevent any contamination from the environment. These tanks can be made of either concrete or plastic and be located below or above the ground surface. The treated greywater can be distributed for irrigation using drip irrigation or a sprinkler system. By using recycled water, urban dwellers can reduce their reliance on expensive piped water and conserve precious water resources.
By combining rainwater harvesting and grey- water recycling, urban dwellers can have a more reliable and sustainable source of water for irrigation. Rainwater can be used as the primary source of water during the wet season, while treated greywater can be used to supplement irrigation during dry seasons. This approach can help to conserve water resources and reduce reliance on expensive piped water.
Simple Techniques for Urban Irrigation:
Once you have a water source for irrigation, choosing the right irrigation technique is crucial for the health of your plants and the efficient use of water. There are several techniques that can be used in urban settings, including drip irrigation, drag hoses and sprinklers.
Drip irrigation is a popular technique that involves delivering water directly to the plant roots through a network of small tubes or emitters. This technique requires low pressures and is particularly useful for conserving water because it delivers water only where it’s needed and minimizes evaporation. Drip irrigation is also beneficial for preventing diseases that can be caused by over- watering foliage.
Drag hoses are another irrigation technique that involves dragging a hose along the ground and manually placing it near the plants. This technique is labor-intensive, but it’s effective for watering larger plants or areas that aren’t easily reached by other irrigation methods.
Sprinklers are the most common irrigation technique and are ideal for watering lawns and large gardens. Sprinklers distribute water over a wide area, making them an efficient way of irrigating larger spaces. However, sprinklers require high pressures and can also result in water waste due to evaporation, runoff, or overspray, so it is important to use them judiciously.
Regardless of which irrigation technique one chooses, it is essential for it to be set up correctly and used regularly to keep the plants healthy. This includes adjusting the system for the right water pressure, choosing the right emitters and placing them in the right position for optimal coverage. Depending on the irrigation system chosen, a booster pump may be required to push water from the storage tank to the emitters, which can help ensure consistent water delivery.
Benefits of Urban Irrigation:
Urban irrigation enables residents in urban areas to grow their own fruits, vegetables and herbs in their backyards, saving them money on food and providing easy access to healthy options. By cultivating their produce, urban residents can ensure that they are eating fresh and nutritious food. For instance, a 6-square-meter area (2m by 3m) can accommodate at least 15 tomato plants or 300 onions, yielding about 100kg of tomatoes or 45kg of onion bulbs, which can feed a family for over sixty days. Vertical gardening is another option that can increase productivity.
Furthermore, urban irrigation promotes food sovereignty by allowing people to eat the food of their choice without relying on external sources. This food is easily accessible in the backyards of homes, improving the overall health of the family. Irrigation can also increase land productivity by providing plants with the necessary water to thrive, leading to higher yields and better-quality produce. This, in turn, strengthens local food systems and economies, helping to combat food insecurity.
Lastly, irrigation can help maintain green spaces in urban areas, which are essential for various reasons, such as improving air quality, reducing the urban heat island effect, and providing habitats for wildlife. Even in areas with limited rainfall or water resources, irrigation can help keep these spaces green and vibrant.
By using water more cost-effectively through urban irrigation, one can reduce water bills, conserve water resources and promote healthy plant growth. Whether one chooses to use rainwater, recycled water or a combination of both, it is important to choose the right irrigation technique and set it up correctly. By taking action and implementing some of the strategies and techniques discussed in this article, you can make a positive impact on your household and the environment.
Eng. Enyetu Joshua
Irrigation Engineer, Akvo International