Dipangkar Kundu
Agricultural Engineer, Agriculture Office, Department of Agricultural Extension (DAE),
Joypurhat-5900, Bangladesh
Phone no: +8801713200826
Web site: [email protected]
Abstract
Agriculture resource planning in Bangladesh carried out without adequate knowledge and information of the specific area. Since, with small amount of irrigated land to feed the overly populated people of the country, precise planning is necessary. This leads to step forward towards a system with updated and enlarged data. The technology, Geographical Information System (GIS) can play an active role by ameliorating the existing system and finding the required information.
This paper describes the application of GIS in minor irrigation projects for assessing the status of irrigation equipment and their irrigated area in context of arsenic and ground water level. Study area includes division wise coverage of the whole Bangladesh. It presents findings generated through the GIS software and documents-based research that indicate arsenic contamination and ground water level has a major impact on minor irrigation. Declination of the Static Water Level observed due to extensive use of mechanized equipments. This paper suggests further developmental study detailing the impact on agricultural environment in order to formulate proper planning and the development of minor irrigation.
1. INTRODUCTION
Bangladesh is predominantly an agricultural country; one third of her national income (GDP) comes from agricultural products. Agriculture is the mainstay of the economic life of Bangladesh. On the other hand, it is the most densely populated country of the world with more than 1936 people living per square mile. Her cultivated land areas are much less in comparison with her population. Chronic food shortages due to various known constraints to normal food grain production under rain fed condition, called for modernization of agriculture and this gave rise to introduction of minor irrigation units such as low lift pumps or surface water irrigation in first case and then Deep Tube Well (DTW), Shallow Tube Well (STW). Besides these, Treadle pumps, Power pumps, Bamboo tube wells, Artesian wells, Dug wells are also used for irrigation in different ways.
Traditional methods of irrigation like as Dons and Swing baskets are very common picture in our country. The combined contribution of all the equipment in minor irrigation is not minor, rather major; more than 90% of the irrigated land of the country is covered by minor irrigation. Minor irrigation introduction has increased food grain production about three times in last three decades. It is playing a significant role in Rabi season especially for the “Boro” production. Different types of irrigation equipment are used in this season to grow more food. The no of irrigation equipment, which are used in “Boro” season and the total irrigated area, are very much needed for policy planning, advice and assist farmer for development and expansion of minor irrigation. Besides this, the dependency of ground water in case of minor irrigation is a major concern as withdraw of water in dry season resulting availability of river water very much insecure for irrigation. Continuous growing dependence on the under ground aquifers as the source of major water for irrigation in dry season results over extraction of the ground water sources, declines the maximum Static Water Level (SWL) causing great environmental impact. So proper water management is required for the development of irrigation program. The concentration and variations of arsenic in ground water should also be taken into consideration. About 72% country’s irrigation water is met by abstraction of ground water from shallow aquifers, where possible contamination soil and food chain by arsenic is a great threat to development of minor irrigation.
The application of computer system and information technology in handling geographic, spatial or non-spatial data is a necessity. The Geographic Information System (GIS) in coactions with other management process will simplify modeling procedures, easy generation of input data, facilitating analysis and clear visualization by geographical position. The GIS collaboration will accelerate the field of research and development by exploring new avenues of exploratory spatial data analysis that were previously not feasible. This leads to greater understanding and hence to better management for future. Using Arc view GIS, the assessment of irrigation equipments and irrigated land area coverage with ground water deflection, arsenic contamination has been easier, generating new epoch in the decision making. The general aim of this paper is the engagement of the activity that surrounds the appropriateness of GIS in proper planning and management of Minor irrigation from environmental point of view. In this study, an attempt has been made to show the status of irrigation equipment and irrigated area through GIS in relation to ground water level and arsenic contamination
The specific objectives are:
- To implement GIS in meeting development of minor irrigation planning
- To focus the contribution of different irrigation equipments in minor irrigation project
- To know the present trend of minor irrigation
- To relate the arsenic contamination in irrigated area planning.
- To relate the changes of ground water level in relation to minor irrigation.
2. METHODOLOGY
2.1 Data Used
Data were collected from the report book of the minor irrigation survey, 2005 provided by BADC, ground water static level data were also provided by the BADC (Bangladesh Agricultural Development Corporation). The arsenic level data, 2001 at different well depth were collected from the web portal of British Geological Survey. For the study, purposes following data were used:
- Division wise data on irrigation equipment , total area, cultivated area, irrigated area during Rabi season 2005
- Division wise data on maximum and minimum Static Water Level data
- Division wise data on arsenic level at different well depth
The methodology followed by making use of the scanned image map of Bangladesh converted into shape file through preparing a new theme. The study of the irrigated land use pattern, ground water level and arsenic contamination level was done with the help of ArcView GIS 3.3 (Geo-processing extension) and graphical analysis through Microsoft Excel. In this study, the irrigated area coverage was linked with arsenic contamination and static ground water level. Data representing the study were interpreted and the map depicts the changes were prepared for clear visualization. Following layout presents the work done process in Arc View GIS.
Fig 1: Working process
Figure-2 shows the sample out put generated by GIS software of the DTW and STW status in whole Bangladesh.
Fig 2: Division wise coverage of DTW and STW in whole Bangladesh
Figure-3 shows comparison of percentage use of DTW, STW, and LLP (Low Lift Pump) during Rabi season in whole Bangladesh.
Fig 3 Percentage use of DTW, STW, LLP in whole Bangladesh
3. FINDINGS
The main objective of the study was to implement GIS application in minor irrigation sector. Nevertheless, the minor irrigation coverage during Rabi season is not same in every division. Application of GIS shows that only 77% coverage of the total irrigated area in Dhaka and Rajshahi division, 54%, 53% in Khulna, Barisal division respectively and only 37% in Chittagong division. It is found that level of arsenic has a great impact on minor irrigation and is a major concern from environmental point of view. In Sylhet division arsenic level is very much low in comparison to other. The highest level is noticed in Chittagong division while the arsenic level remains moderate in Rajshahi division ranging from 0-2.472 ug/l in greater percentage of the region. Sharp decrease in manually operated pump is noticed so as in their irrigated area. It is higher in Sylhet division up to 68 % of the total and lowest in Khulna division up to 0.5%. Scenario shows long-term dependency on mechanized equipment. In comparison to DTW, it is ascertained that LLP and STW is mostly used. Among these equipments, the power consumption of STW run by diesel is about 81% while by electrical is about 9%. STW coverage in Sylhet and
Fig 4: STW scenario and Irrigated area coverage of the minor irrigation project during Boro season
Barisal division is less comparison to other divisions, its maximum coverage in Rajshahi division while Dhaka and Khulna division remains in the second position. Ground Water SWL (Static Water level) in Dhaka division is noticed maximum 14-20 m while the moderate value remains up to 6 m in average. In Rajshahi division, the moderate value of SWL remains 6-10 m, higher up to 15 m in average. In Chittagong, division SWL is quite low; it is up to 8.66 m in average in most of the districts while in Sylhet maximum is recorded about 5-6m in average.
4. DISCUSSION AND CONCLUSION
Based on the findings by applying GIS on minor irrigation it is observed that there is a trend of enlarging area by minor irrigation mostly in Rajshahi and Dhaka division than others. The major factor contributing to this expansion is the static water level; arsenic level also has its impact too. However, excessive withdrawn of water from these area causing lowering of the static water level creating a negative impact on the environment. In Chittagong division irrigation coverage is low due to higher arsenic contamination in region nearer the Meghna River; though the later part of the Chittagong division might be useful for minor irrigation activity. Besides this, mechanized equipment is playing a significant role in the development of minor irrigation. There is a tendency of increasing both LLP and STW in comparison to manually operated equipment. Increased no of STW was found in Rajshahi division followed by Dhaka and Khulna division but very poor in Barisal division. Again, in Chittagong division the use of LLP is higher, using extensively the surface water source. Higher use of this mechanized equipment has lead to increase in power consumption. STW run by diesel is the top most consumers in the whole Bangladesh and STW run by electricity is the next. Those run by diesel creating harmful effect on the environment by air pollution so as noise pollution. This might be one of the considerable points in planning action strategy from environmental point of view.
Evidence from this report shows that minor irrigation plays both positive and negative role in national economy development through agriculture. Positive in a sense that it is taking the place of Major irrigation covering most of the irrigated area with less investment but it is negative in a sense that it is using more of the mechanized equipment and extracting more of the ground water creating pressure on the natural resource as well as on environment. GIS application to minor irrigation makes assessment of the trend and nature of irrigation in faster and precise way comprising both socioeconomic and environmental factors. Using this system leads to successful mitigation of hazardous agricultural environment and take proper technical decision
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