All living organisms on earth need water for their survival. Water is life; It is an important constituent of any cell either it is a plant cell or animal cell. It has massive importance in multiple spheres of life, and is not only essential to meet the needs of agriculture but also for the industrial, livestock, re-creational and domestic utilization. About 70% of Earth is covered with water which means that only 30% of Earth consists of solid land. Out of total water content on Earth, 97% is saline water present in oceans and seas. Whereas, the rest of 3% is fresh water out of which 2% is locked in glaciers and polar ice caps and the remaining 1% is present above ground as streams, rivers, lakes etc. Despite of this, 1.2 billion people around the world do not have access to clean drinking water; quantity of fresh water is still low and it almost affects every continent. Today, water is considered as ‘Liquid Gold’ due to increasing cost of irrigation projects and limited supply of good quality water. Along with the decreasing quantity of usable water, it is also becoming poor in quality due to several factors such as, pollution, over-consumption, unsustainable use, climate change and global warming.
Irrigation and its importance
Water acts as a substantial instrument in irrigation, as no seed can be reached its maturity, and no seedling can come out from seed without the mercy of water. In the absence of rain, irrigation is practiced in the agricultural field. It is the artificial application of water to the plants to fulfill the water requirement of plant; conserve the soil moisture and help the plant to grow properly. Globally, it is estimated that about 70% of fresh water is used to irrigate 25% of the world’s croplands with supply 45% of global food. Irrigation is important because it provides water in sufficient quantity to the yield, that’s why it flourishes agricultural and horticulture crops. Moreover, irrigation is necessary when plants cannot satisfy all their water needs through natural precipitation this practice is also called deficit irrigation. Therefore, an ideal irrigation effort aims to cover the deficit between a crop’s optimal water needs and what it can take up through natural means. Additionally, to find a most appreciable method to irrigate the fields there are some factors that influence irrigation method that are soil type, soil depth, topography of land, water sources, water seepage pattern, climate (including temperature, wind, humidity, rainfall etc), local traditions & skills, crops to be grown and many other factors.
Irrigation techniques
There are many ways to irrigate a field. They include flood irrigation, furrow irrigation, sub-irrigation, sprinkler irrigation, drip irrigation and basin irrigation to name a few. All the techniques are described below in Table 1. Furthermore, layout is very important in selecting a suitable method for irrigation. Application of water to the cropland by different types of layouts is called methods of irrigation.
| Table 1: Types of irrigation systems | |
|---|---|
| Techniques | Description |
| Manual irrigation | Water is distributed across land through manual labor and watering cans. This method is very labor intensive and is less efficient. |
| Localized irrigation | Water is distributed under low pressure, through a pipe network and applied to the each plant. This method is less efficient. |
| Flood irrigation | Overall piece of land is wet with water. One of the oldest, simple, cheap and widely used method. But the biggest problem or downside in this method is that the sheer amount of water is used. |
| Basin irrigation | Water is applied rapidly to the entire basin and is allowed to infiltrate. In basin irrigation if the basin is not level the higher elevation areas will receive less water than the lower areas. |
| Furrow irrigation | Only the furrows become wet or ground which contain crop. Furrow or border irrigation can be used where water can be fed into small channels or strips of land. Water flow rate must be adjusted in this method and it requires greater labor than the other techniques. In this method soil erosion is increases as field slope and inflow rate increases. |
| Sub irrigation | Water is delivered to the plant root zone from below the soil surface and absorbed upwards. Water is distributed across land by raising the water table, through a system of pumping stations, canals, gates and ditches. Moreover, this method is very effective in areas with high water tables. |
| Surface irrigation | Water is distributed over and across land by gravity and no mechanical pump is involved in this method. It involves the application of water by gravity flow to the surface of the field. Alternatively, Surface irrigation is the easiest and least costly method, but is usually highly inefficient only less than 10% of the water is taken up by the plant. |
| Sprinkler irrigation | Water is distributed by overhead high pressure sprinklers or guns from a central location in the field or from sprinklers on moving platforms. It is very effective method. |
| Drip irrigation | Water is provided drop by drop to the root zone. It is highly effective and efficient method. It also maintains the field capacity level without any water stress. Furthermore, in this method water runoff and evaporation rate both are minimized. |
| Lateral move irrigation | Water is distributed through a series of pipes, each with a wheel and a set of sprinklers which are either rotated by hand or with a purpose-built mechanism. The sprinklers move a certain distance across the field and then need to have the water hose reconnected for the next distance. |
| Center pivot irrigation | Water is distributed in a field by a system or sprinklers that move on wheeled towers in a circular pattern. It is very efficient method. Furthermore, this method is common in flat areas. |
Water scarcity’s pressure on the limited water resources
Water scarcity is the lack of sufficient available water resources to meet the overall demands of water usage within any region. It is a globally significant and accelerating problem that immensely affects the water needs of both human as well as natural environment. Many countries are going through alarming water scarcity. So, it has become necessary to save water by adopting a suitable method of irrigation that will use less amount of water and provide better efficiency. Water scarcity is not only hindering the growth of food production, but also harming human health, environment and also exerts pressure on the economic development. Water scarcity condition prevail in any region or area due to lack of rainfall, lack of suitable infrastructure, lack of efficient resources, drought, desertification, water shortage, pollution. According to “World Resources Institute’s Aqueduct Water Risk Atlas” 150 countries are facing extremely high water stressed condition, in which top 15 countries are shown in the Table: 2.
| Table 2: Extremely high water stressed countries | ||
|---|---|---|
| Top 15 countries in the world facing extremely high water stressed condition | ||
| Rank | Country | Water stress |
| 1 | Qatar | Extremely high |
| 2 | Lebanon | Extremely high |
| 3 | Israel | Extremely high |
| 4 | Iran | Extremely high |
| 5 | Jordon | Extremely high |
| 6 | Libya | Extremely high |
| 7 | Kuwait | Extremely high |
| 8 | Saudi Arabia | Extremely high |
| 9 | Eritrea | Extremely high |
| 10 | United Arab Emirates | Extremely high |
| 11 | San Marino | Extremely high |
| 12 | Bahrain | Extremely high |
| 13 | India | Extremely high |
| 14 | Pakistan | Extremely high |
| 15 | Turkmenistan | Extremely high |
| Source: Report issued by the world resources institute (WRI) | ||
Efficient irrigation practices
Apart from simple irrigation, another term is “efficient irrigation”. It is the controlled application of the water to the cropland in a required quantity at a required time to get optimum yield. Another important term is “irrigation water efficiency”. It is the ratio of the amount of water consumed by the crop to the amount of water supplied through irrigation by using different types of efficient techniques such as drip, sprinkler and mechanized irrigation. Nowadays, the use and extraction of water is increasing day by day in order to fulfill the overall needs of large human population and environment. Irrigation techniques like flood irrigation are still practiced in today’s world, but nowadays they are not suitable due to the current water shortage. That’s why, other efficient irrigation techniques are used to minimize the loss of water. Among them, three are considered as more efficient that are drip, sprinkler and mechanized irrigation systems. Such modern or smart irrigation practices and technology not only produce more but also produce higher quality plants with less water. Additionally, we can get further elevate efficiency at the local, regional and farm levels through the use of alternative sources of water for irrigation such as rainwater harvesting and utilizing treated waste water with the use of modern technology.
Furthermore, the main factors that influence the efficiency and effectiveness of irrigation practices and make a method more efficient are climatic conditions, soil type and structure, plant type, and the irrigation techniques applied. For a given location and climatic and soil conditions, the efficiency of water irrigation practices can be improved by making the right decisions regarding crop type, irrigation scheduling, irrigation method, soil enhancement measures and source of water.
Most efficient irrigation techniques are:-
Drip irrigation:
Drip irrigation delivers water through the use of pressurized pipes and drippers that run close to the plants and that can be placed on the soil surface or below ground. It is also known as micro-irrigation. Now-a-days this method is widely being used because it is very efficient method; providing water only to the immediate root zone of each plant. This system also allows precise application of water soluble fertilizers and other agricultural chemicals. Drip irrigation is reported to help achieve yield gains of up to 100%, water savings of up to 40-80%, and associated fertilizer, pesticide, and labor savings over conventional irrigation systems. Such systems usually last up to 10 to 15 years before they need to be replaced. Moreover, this technique can have different levels of sophistication and costs. Drip irrigation systems that are operated by solar-driven pumps are a particularly promising alternative for the region having intensive solar light. This method can also be used to irrigate sloping or irregularly-shaped land areas. Water use efficiency of well managed drip irrigation system is 95 to 100%.
Sprinkler irrigation:
Sprinkler irrigation is a method of applying water to the agricultural land in a manner that mimics natural rainfall. Water is pumped through pipes and then sprayed onto the crops through rotating sprinkler heads. These systems are more efficient than surface irrigation, because water application is more controlled. However, they are more costly to install and operate because of the need for pressurized water. Conventional sprinkler systems spray the water into the air, losing considerable amounts to evaporation. Most efficient method to irrigate the uneven land for agriculture. Sprinkler systems have 80 to 85% water use efficiency. Field life of sprinkler irrigation system is about 20 years.
Mechanized irrigation:
Mechanized irrigation uses center pivots or linear machines to irrigate land. In this method, water is uniformly applied to a large area with little labor. Furthermore, center pivots or linear are less expensive to install on large fields, even installed in one and two days and have a higher resale value than the drip irrigation systems. This is often preferred for operations where frequent crop rotations are used. Moreover, they are also preferable in fields with sandy soils but can be modified for nearly any type of soil by changing application rates, tires and sprinkler types. Mechanized irrigation methods can be used in hilly land and also used to apply chemicals and fertilizers to your fields. Center pivots or linear machines have excellent field life, often 20 years or more.
Concluding this, we shouldn’t hit our life by using water in unsustainable manner. It is need of hour to save the water for the agriculture irrigation purpose, industrial purpose, livestock, domestic and recreational purpose. Using efficient irrigation practices to fulfill agricultural demands, proper management and cleaning of the whole irrigation system are very important to maintain the overall efficiency of the irrigation systems. Efficient irrigation management is required to achieve the goal of best irrigation in field without exerting pressure on the limited water supply. Such innovative irrigation practices not only enhance the water efficiency, but also provide economic advantages and reduce environmental burdens.
“Install the best, service the rest”.
[box type=”note” align=”” class=”” width=””]The author Sadia Hassan Sherani is an environmentalist – wrote several review papers (published in International Journal’s), newspaper articles and online articles[/box]