Irrigation

Irrigation is an incredibly important part of creating efficient and sustainable agriculture. Currently, Bangladesh uses fertilizer in its irrigation water to increase productivity of rice crops, and this has had large improvement in crop yield, from 12 million tons of rice in 1973 to 35 million tons in 2015.^[1] Without planned irrigation systems, crops will suffer during droughts, and poorly implemented irrigation can increase the salinity of soils. Especially in the northern regions of Bangladesh, droughts require irrigation to come from groundwater sources, and studies have shown that daily use of water will increase due to climate change, resulting in a net increase of water withdrawn from the water table. According to the government’s Bangladesh Delta Plan 2100, “due to climate change, irrigation water demand is projected to increase from less than 1% for 2030 in average condition, to maximum 3% for 2050 in dry condition.”^[1] This increase in demand could put considerable stress on the water resources for that region and will impact the entire country because crops produced in the north are distributed throughout the entire country, so crop devastation in the north will create food scarcity and high food prices everywhere. A study done on boro rice, the most common rice crop in Bangladesh, shows that though farmers are shifting to this low-risk crop, they will also require a higher irrigation rate and a higher cost of water for farmers for the same yield.^[2] The study used climate models to predict how rice and soil would be affected by rising temperatures and found that the daily water demand will increase by 9% in the northern district studied^[2].

The United Nations and the government of Bangladesh previously issued the United Nations Development Programme for Bangladesh,^[3] and one of its programs was specifically designed to improve irrigation capacity of drought-prone regions, especially those like the Barind in the northwest. This program constructed mechanized tube well based irrigation on a large scale and had strong effects on increasing water availability for dry regions. The program allowed previously infertile areas to begin producing fruits, vegetables, and higher-yield species of rice.^[1] However, as the irrigation system became privatized, the system increased the stress on groundwater supply as private users overdrew water from the water table.^[1] The plan was a decent start to addressing the irrigation concerns of the country, but in the future, it is essential for the government to exert more control over water and irrigation-related issues in order to prevent issues like this one.

As stated in Bangladesh Delta Plan 2100, two steps need to be taken to ensure water security for agriculture and human consumption: supply management and new irrigation sources, and demand management and efficient water use.^[1] To address the first step, the Delta Plan proposes drawing new irrigation sources from major and regional rivers in order to decrease demand from groundwater sources. In addition, instead of dumping wastewater back into the environment, it could be mildly treated and reused for irrigation.^[1] Drawing from these alternative water sources, rather than from wells or mechanized tubes, would reduce stress on the water table. This solution would also require more extensive water sanitation strategies as surface water is more likely to be polluted by salts, arsenic, and other pollutants, but better water treatment infrastructure is well worth the cost.

To address the second step of ensuring water security, Bangladesh needs to implement more efficient irrigation practices for their rice crops that will reduce water use and lower the drain on groundwater sources. A study on rice crops in China found an irrigation timing system that could reduce water usage by up to 41% with a 15% increase in yield.^[4] This process requires controlled irrigation, meaning only a certain amount of water is used, varying by stage of crop growth. This strict control may be difficult to maintain in an increasingly erratic climate, but it will be very effective in times of drought, especially in northern Bangladesh. Maintaining strict control of irrigation schedules could be achieved by soil moisture sensors (see below). The specifics of the irrigation technique as found in the Chinese study are as follows: after seeding, 5-25mm of water is maintained above the soil. After the regreening phase, no water layer above the soil surface is allowed, and the soil should be saturated by 60-100% moisture. By manual measuring and adjusting of the soil moisture, it would be possible and feasible to maintain this irrigation level, even with erratic weather patterns.^[4] Bangladesh should educate its farmers to follow this irrigation strategy and fund more research to determine if there are better irrigation techniques for the Bangladesh region specifically. This will both increase crop yield and reduce the stress on groundwater sources, allowing this water to be used for other required purposes.

Monitoring irrigation for optimal watering times can be done manually, as described above, but also using technology. Another solution to improving water efficiency for irrigation is to put sensors in the soil that can monitor moisture levels, salinity, and soil temperature , allowing farmers to adapt their irrigation schedule to the changes in weather patterns. Soil moisture sensors already exist and are used in other areas of the world to improve watering schedules [Figure 1].

Figure 1: Moisture Sensor called the “Irrigation Stick” Being Tested in Myanmar

Source: Ideo.org, FastCompany^[5]

For soil sensors to work, the sensors must be buried in a few locations throughout the field: one near the surface, one at root-level, and one below the roots. These sensors then relay the information to a data logger, which the farmer can use to learn how the water is travelling through the soil and when is the most optimal time to water. One sensor, developed by SEED LLC by UC Davis, costs $50-100 for the sensors and data logger, and SIM card.^[6] This sensor, as well as the sensor pictured above [Figure 1], have been successful in tests on crop yield in their respective countries. The Bangladesh government should subsidize or fully fund the implementation of soil sensors by farmers, and startups that have been implementing sensors in other developing countries should expand their companies to installing sensors in Bangladesh as well.

This two-pronged approach to irrigation improvement–drawing water from alternative sources along with increasing the water efficiency of irrigation systems–will decrease the stress on groundwater sources in Bangladesh, allowing for higher water security for drought-prone areas. Ensuring that Bangladesh has a stable agriculture system with high yield and efficient resource input will greatly improve the country’s resilience to climate change, especially as weather patterns become more erratic.

By Sarah Weidman

References

1. Bangladesh Delta Plan 2100 (pp. 1-714, Rep.). (2017). Bangladesh: General Economics Division, Bangladesh Planning Commission.
2. Shahid, Shamsuddin. (2011). Impact of climate change on irrigation water demand of dry season Boro rice in northwest Bangladesh. Climate Change 105, no. 3-4, (433-4553).
3. United Nations Development Plan for Bangladesh. (2017). Retrieved from http://www.bd.undp.org/content/bangladesh/en/home.html
4. Shizhang, Peng (1994). New water consumption pattern of rice under water-saving irrigation. Irrigation and Drainage Systems 8, (97-108).
5. Shiller, Ben. (2015). Ideo.org Is Bringing Low-Cost Precision Agriculture To Developing Countries. Retrieved from https://www.fastcompany.com

6. Sim, Rachel, Sarah Plummer, and Mounir Fellahi. (2015). Assessment of Potential Markets for Soil Moisture Sensor in Tanzania. UC Davis D-Lab, (1-26).