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Renewable Water Resources and an Overall Water Demand-availability Analysis for Bangladesh

Shovit Barua
Graduated Student
Chittagong University of Engineering & Technology, Bangladesh

Md. Reaz Akter Mullick
Associate Professor
Chittagong University of Engineering & Technology, Bangladesh

Ayan Barua
Graduated Student
Chittagong University of Engineering & Technology, Bangladesh

Abstract/ Executive Summary:

Freshwater is the major source of water for human consumption. Renewal rate of fresh water resources determines the availability of fresh water for human use. Renewable water resources are the total amount of water resources which is generated through the hydrological cycle and is often measured for a country on annual basis. Availability of sufficient quantity of water throughout the year is necessary for food production, economic development and life. In a general view, a country like Bangladesh may often be treated as water abundant. But the situation is different when the water demand and availability in a short term basis are compared. This study quantifies the seasonal distribution of renewable water availability, sectorwise monthly consumption pattern and ultimately the water conservation required at specific month to counteract seasonal water scarcity in Bangladesh. Water demand of the main three sectors; agricultural, domestic and industrial are computed for the specific year. The agricultural water demand is estimated based on hydrologic and agronomic characteristics using in the modeling approach of Rosegrant and Cai (2002). The industrial & domestic water demand is estimated on the basis of secondary data. The availability of internal renewable water resources is estimated using long term monthly average precipitation pattern whereas that of external renewable water resources is estimated based on the transboundary river flow pattern. The greatest drain of water supplies is agriculture (40.08 km³ /year), followed by household use (4.14 km3 /year), and industry and energy (1.03 km³ /year). The water demand is found to be very high from November to March and the maximum demand occurs in March (12.44 km³). Water shortage is found in the months of January to March. The study suggests a water management plan for reserving 22.25km³ water from November & December which can mitigate the shortage from January to March. The outcome of this study emphasizes on the necessity of adopting suitable mitigation strategy against water shortage.

Keywords: Renewable water resources, Seasonal variability, Water availability, Water scarcity

Location: In Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Water management, Water productivity

Objectives:

The following objectives: 1) quantifying sectorwise water demand within the country on a monthly basis, 2) simulating monthly water demand and supply for investigating the gap between them and subsequently suggest policies regarding water management for building resilience against water scarcity.

Methodology:

The monthly distribution of renewable water availability or exploitable renewable water resource can be calculated as follows: Available RWR = ERWR + IRWR − EWR (1) Where, ERWR is external renewable water resources, IRWR is internal renewable water resources and EWR is environmental water requirement. The transboundary river discharges mainly constitute the external renewable water resources. The mean monthly discharge of Ganges (1950-2004) and Brahmaputra (1953-2004) at Hardinge bridge and Bahadurabad stations respectively are obtained from Jian et al (2009). Other transboundary river discharges are estimated based on the Ganges-Brahmaputra monthly discharge pattern. The generation of internal renewable water resources of the country is mainly from the precipitation within the country. Based on this, the internal renewable water resources is distributed among the months as per monthly rainfall proportion of the country. Environmental water requirement, which is required to maintain a fair condition of fresh water ecosystem, ranges from 20-50% of the mean annual river flow (Smakhtin, 2004). We considered 20% of the Ganges-Brahmaputra-Meghna (GBM) mean annual discharge into Bay of Bengal as the minimum EWR. Water Demand: Agricultural water demand consists of water demand for irrigation, livestock, etc. For Bangladesh, livestock and other agricultural water demands are very negligible compared to irrigation water demand. So, irrigation water demand is considered as agricultural water demand in this study. The monthly irrigation water demand is calculated in 3 steps: Monthly irrigation water demand is assessed using a modeling approach based on agronomic and hydrological characteristics of the country (Cai & Rosegrant, 2002). A countrywide approach is followed with the country divided into 7 hydroloical regions. The necessary data of monthly maximum and minimum temperature, humidity, wind speed, precipitation and sunshine hour of 35 stations were collected from Bangladesh Meteorological Department. The monthly data of the respective stations within each region are averaged to get the mean monthly data for that region. The monthly reference evapotranspiration (ET0) in each hydrological region was calculated by using PenmanMonteith method. The effective precipitation was estimated by USDA Soil Conservation Method from the mean monthly precipitation data. Among the 7 hydrological regions, the salinity problem in soil and irrigation water is very threatening in southern coastal parts of Bangladesh (South-west and South-central hydrological zones in particular, apart from few parts of South-east and Eastern Hill regions).The dry season and premonsoon months suffer maximum soil salinity (D. Clarke, 2015 ; H. M. Rasel, 2013). Water Demand Scenario of Bangladesh: The total water demand in the year 2012 is found to be 45.26 km³ which was 35.87 km3 in 2008.It is generated from mainly three sectors: agriculture 40.08 km³ (88.57%), domestic 4.412 km³ (9.15%) and industrial sector 1.03 km3 (2.28%). The maximum demand occurs in March (12.44 km³ ) and the minimum demand occurs in June (0.43 km3 ).Agricultural water demand dominates the monthly total water demand except the month June. Agricultural Water Demand: Agriculture is the major water using economic sector while rice is the most water consuming crop (consumes 78.45% of the total water demand). The net irrigation water demand found is 28.05 km³ which was 24.56 km³ in 2008.The agricultural withdrawal is found 40.08 km³ which was 31.5 km³ in 2008. Domestic Water Demand: The seasonal variation of domestic water demand is very significant. It shows two patterns. The monsoon season (June-October) demand is 0.327 km³ and dry season (November-May) demand is 0.358 km³ . The total domestic water demand in 2012 is found to be 4.12 km³ whereas it was 3.6 km³ in 2008. As the population is increasing day by day, the domestic water consumption will go up gradually. Industrial Water Demand: Uniform industrial water demand is found throughout the year and the monthly demand is 0.086 km³ . The total industrial water demand in 2012 is 1.03 km³ whereas in 2008 it was 0.77 km³ . As the industrial production growth rate in 2012 is higher than that was in 2008, it is logical that demand is increasing in proportion. Renewable Water Availability: Maximum internal renewable water generates in month July (22.81 km³) while the maximum external renewable water generates in August (245.42 km³ ). Environmental water requirement has 3 patterns (20.42 km³ , 18.45 km³ and 19.77 km³ ) based on month duration. Renewable water availability varies throughout the year. January, February and March are the three months having very low water availability with February having the lowest (.67 km³ only) available water.

Source of Information: Proceedings of the 3rd International Conference on Civil Engineering for Sustainable Development (ICCESD 2016), 12~14 February 2016, KUET, Khulna, Bangladesh (ISBN: 978-984-34-0265-3)

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Water use for livelihood, agriculture, industry and infrastructure has increased during last few decades in Bangladesh. Above all, due to increase in population, per capita availability of water is declining. Water availability is not optimum when required for various sectors to their efficient utilization. There are many agro climatic variables which governs water resource in Bangladesh such as water conflicts, groundwater extraction, irrigation based rice farming, and inadequate water flow in rivers during dry and of seasons, variability in rainfall events and inefficient irrigation. The cumulative effects of these factors have led to water scarcity situations of varying extent in different parts of Bangladesh. The study shows that water resources have become inadequate and scarce in dry season from January to March. But there exists excess available water in rest of the months around the year. Scarcity of fresh water can directly affect the long-term prospects for sustainable development. Excessive nonrenewable water extraction during dry season from deep aquifer is causing water table lowering and making groundwater more unavailable. Due to unavailability of water, cropping pattern of the country is also changing and facing yield reduction. Without an adequate water supply, factories depending on water may have to be closed down temporarily; workers may be unproductive; fisheries may be destroyed. How to relieve the worsening water crisis has become a major common-concerned strategic issue from agricultural perspectives in the 21st century for Bangladesh. In order to build resilience against water shortage related problem, it is necessary to know the durations as well as the amount of water shortage. This study can serve as the base of sustainable water use and management related planning, projection and action. For further research it is important to assess the spatiotemporal variability of fresh water availability and how much water can sustainably be used in a certain country without adversely affecting the ecosystem.

Knowledge Management: Report/Proceedings