Flood Control and Irrigation Systems
The flood control and irrigation systems have several functions. Surge flooding is the most effective flood control method, as it releases water in intervals, allowing it to soak into the soil. The water then is released for reuse. Combined with irrigation, these two methods minimize flood damage and maximize irrigation. Besides flood control, these systems also help in enhancing the beauty of landscapes and water resources. For more information about flood control and irrigation systems, read on!
Impacts of floods
Floods are devastating natural disasters that destroy physical infrastructure that is vital for agriculture and the food supply chain. This destruction deteriorates food availability, access, and stability. Floods can damage transportation systems and infrastructures for emergency food aid, which can be a significant problem for communities that rely on agriculture for food. Furthermore, the availability and utility of food depends on how a community can transform it. The following are some examples of the impacts of floods on agriculture.
In Ghana, floods have long been a problem for farmers. In the northern regions of the country, floods have a direct impact on crop production and food security. Floods have a pronounced impact on livestock and farm crops. The Bagre Reservoir spills water upstream from Burkina Faso, causing extensive floods in several districts. Floods also damage irrigation systems and water supply infrastructure.
Flood irrigation is an excellent way to boost crop yield and productivity, but at the same time, it can also deplete soils of dissolved salts, which are detrimental to plant growth, yield, and water absorption. This can lead to the development of monocultures and a higher risk of several mosquito-borne diseases. Many studies have linked flood irrigation with increased malaria incidence. Flood irrigation could also reduce the spread of disease by increasing the number of livestock and wild animals in areas with high rainfall levels.
In the same way, LULC and irrigation can alter the distribution of disease. These changes depend on the ability of pests to establish niches in floodplains and how much local populations are able to protect the region. The study in Garissa and Tana River counties included a study of LULC changes in agricultural land. The researchers also compared the extent of change in vegetation and cropland on floodplains in the two counties.
Methods of minimizing flood damage
A large percentage of rainwater becomes runoff, and while some is absorbed by grass and ponds, the rest travels across land as surface runoff. The runoff is increased when rainfall exceeds the amount of water that can be carried by stream channels. As much as 30 percent of all precipitation can become runoff, and even more is exacerbated by melting snow and soil erosion. Fortunately, there are methods that can reduce flood damage and make irrigation more sustainable.
One of the oldest methods of irrigation is flooding. While flooding is mostly practiced in areas prone to extreme summer heat, it can be used in home gardens, even for small plots. In order to make floods beneficial, the land should be level and have sufficient clay content, as well as have sufficient drainage. The water should not remain in the soil for more than a few hours. Using this technique, floodwater can be used to irrigate crops, fill drinking water ponds, or grazing grounds.
Natural control method
Agricultural fields need a predictable and scheduled water supply, and flooding can be a great benefit for both people and nature. Flood irrigation can provide the soil with the water it needs to grow crops. In fact, floods are an effective way to recharge ground water and graze livestock, and floodwater from mountain catchments can be used to fill drinking water ponds and irrigate fields. Floods are also an excellent way to control soil salinity.
Although natural flood management has many definitions in the literature, the process is generally understood to be an overall approach to hydrology and flood management. These natural flood management techniques use a holistic approach to mitigate flood risk by replicating and enhancing natural processes. The Environment Agency categorizes natural flood management techniques in the United Kingdom. The benefits of natural flood management are often outweighed by the costs of the projects. Soil scientists can use these models to determine how effective flood control methods are in specific areas.
Flood control techniques include terracing slopes to slow the flow of floodwater, planting trees and plants, and building dams and reservoirs. Flood control also includes coastal management methods to protect areas from erosion. Coastal management techniques include the use of sandbags and drainage channels. Coastal management practices are becoming increasingly important because of climate change. Rising sea levels will cause erosion and damage to beaches. The effects of climate change will be felt for decades to come.
While hydraulic models are considered to be an alternative to natural flood control, they are not economically viable. Moreover, they require the use of cross-section data across flood routes. Additionally, they do not provide an adequate solution for irrigation projects because they do not account for channel geometry. In fact, there is no scientific evidence to support the use of hydraulic models for flood routing. However, some researchers suggest that these models can be used to predict the hydrographs of floods without using any physical data.
Constant-volume discharge method
The Constant-volume discharge method for flooding and agriculture is an important method for managing floodplains and is used in hydropower projects to plan irrigation and flood control. The method can be applied to a variety of catchments. In some cases, the discharge is variable. The amount of water added to a catchment is determined by the available flow data. Flow data in adjacent catchments can be used to estimate the discharge of a basin.
The process for estimating discharge is not straightforward and requires the input of specialists. Flow gauges measure instantaneous stage and water depth at periodic intervals and use a rating curve to translate these values into discharge. By measuring the velocity and water depth, however, the discharge is estimated. In the United States, the USGS is the primary federal agency for floodplain hydrology. This methodology uses a variety of hydrological and meteorological data.
Another method of estimating river discharge is the Manning equation. The Manning equation uses a parameter called Hydraulic Radius that varies with the cross-section of open channels. Hydrological models can be calculated using different mathematical equations, including Pythagoras’ theorem. In Figure 5 below, a typical open channel cross-section is illustrated. The Kunur River has a trapezoidal cross-section.
When using the Constant-volume discharge method for flooding and agricultural production, we must take into account location-specific factors when choosing a flood type. Weighing these factors will help us decide on the best flood type for our purposes. For example, if the floods will occur more frequently than we expected, we can determine the design flood with the help of a frequency analysis. However, we need to remember that there are many non-hydrologic considerations that should be considered before deciding on a flood type.
Modern pressurized irrigation systems
Water scarcity is a major factor that has motivated the development of various irrigation technologies. These irrigation systems can be categorized into surface irrigation, subsurface irrigation, or sprinkler irrigation. Sprinkler irrigation uses less water than basin irrigation and is more efficient in both conveyance and application. The efficiency of drip and sprinkler irrigation is 100%, while basin irrigation only manages to achieve a conveyance efficiency of 60%-70%.
The main data used for designing a drip irrigation system are aerial photos, river water levels, and rainfall. During the 3.5 month field work, interviews with farmers, and topographic survey were conducted. After this, data sets were analyzed to create maps and other data sets that form the base information for the irrigation system design. These data sets will be used to calculate the amount of water needed for each irrigation level.
Depending on the nature of the flood situation, some people may not want their water to be diverted to the floodplains. To prevent this, the irrigation system should be designed to limit the amount of water entering the floodplains. The new irrigation system will not hinder existing fishing activities. Nevertheless, the effects on the right bank are unknown. Further studies are necessary to determine the best method of flood control in this region.
Irrigation systems are designed to be managed by an appropriate organization. In developing countries, this work is generally devolved to farmers’ associations or farmer organizations. Farmers and future users are expected to carry out a significant portion of implementation. If the government is not willing to finance the irrigation system, irrigation schemes can be the answer. So, the question remains, who should be in charge of the irrigation systems?