Feb 6, 2012

Alternate Water Source Investigation in Barind Tract

Figure 1: Barind Tract 
Barind Tract is situated in the north western part of Bangladesh. It is a semi arid region. Soil structure is different in this region. This is the largest Pleistocene physiographic unit in the whole Bangladesh floodplain. It covers an area of about 7,770 km2. It has long been recognised as a unit of old alluvium, which differs from the surrounding floodplains. This physiographic unit is bounded by the Karatoya river to the east, the Mahananda river to the west, and the northern bank of the Ganges River to the South. A lower fault scarp marks the eastern edge of the Barind Tract, and the Little Jamuna River (Jamuneshwari), Atrai River and Lower Punarbhaba rivers occupy fault troughs. The western part of this unit has been tilted up; parts of the western edge are more than 15 m higher than the rest of the tract and the adjoining Mahananda floodplain. The southern part of the main eastern block of the Barind Tract is tilted down towards the southwest and passes under lower Atrai basin sediments in the south. 

Figure 2: Rainfall trends and GW depletion
near Tanore


Barind tract is higher than adjacent flood plain. For this reason very few river has flown through this region. Water availability only depends on ground water. Barind Multipurpose Development Authority (BMDA) has undertaken mass activities based on GW. As a reason extraction rate of GW has exceeded recharge rate. In last 10 years about 10~12 m of mining of GW has observed in this region. Though this tract is bounded by several water bodies, but due to different soil characteristics, recharge rate is generally slow compared to other tracts of Bangladesh. At this rate it can be assumed that after next 30~40 year, GW table will lower to an unextractable level or the cost of extraction will increase to a great extent. An alternate surface water source is required to cope with this adverse situation. 

Figure 3: Rainfall trends and GW depletion
near Noahata 
The study area is situated in the barind area of Rajshahi and Noagaon districts. The area to be covered in the study is shown in Figure 1. The area includes a total of seven upazilas, out of which five in Rajshahi district namely Durgapur, Mohanpur, Baghmara, Tanor and part of Paba Upazila; and two upazilas in Naogaon district namely Niamatpur and Manda. 
River System of Adjacent Study Area: 

The river and road system of Barind region is provided in Fig. 4. 

Surface water model simulation has been carried out under Barind to assess the dry period water availability in major rivers of the study area. The following major rivers have been included in the model 

o Ganges 
o Atrai 
o Siva-Barnai 
Figure 4: River System in Barind Tract 
Ganges River 
The Ganges River enters into Bangladesh in Chapai Nawabganj District at 18.0 km below Farrakha Barrage and then flows as common border for about 106 km. A major flow diversion of the Ganges takes place from Farakka Barrage. This diverts flows. Although the flow is diverted, this river can represent the major source of dry period irrigation water supply in high Barind areas. 
Figure 5: Ganges River near Gopalpur Pourashava 
Atrai River 
The Atrai River enters into project area at Simulbari from India. This river flows from north to south. At Manda, Sib-barnai River has bifurcated from Atrai. The bifurcated point had been closed by embankment. 
Figure 6: Atrai River 
Siva-Barnai River 
The river flows from north to south. The river almost dries up during summer, except in the depression area along the river. This River is flowing through the eastern side of Tanore Pourashava. Water is not available throughout the year. There is no significant natural Khal flowing through the Tanore Pourashava area. However there is a beel named ‘Beel Joania’ with an area of 0.62 sq. km. 
Figure 7: Siva-Barnai River in Dry season 
Surface Water Availability 
A model has been developed in MIKE11 to assess the surface water availability in this region. North West Region Model (Source: IWM) of Bangladesh is used for this purpose. The North West Region Model (NWRM) is bounded by the Jamuna River to the East, the Ganges to the south, and the international border to the north and west. NWRM covers a catchment area of around 32,600 km2, spanning between longitudes 88°00' E to 89°50' E and latitudes 23°45' N to 26°45' N. Frequency analysis for monthly minimum flow data from 1985 to 2009 for some selected locations in the major rivers have been carried out. Table 1 shows the dry period 80% dependable flow in different rivers of the study area. It is observed from Table 1 that water resources available at Atrai and Sib-Barnai are very limited. For sustainability of a river, it is not feasible to conserve or utilize all available water resources. Useable resource has been considered as 70% of the available resources and 30% of the available resources have been taken into account as "in-stream flow requirement" in the river.
Table 1: 80% Dependable Flow during dry period 
River
80% Dependable Flow (m3/s)
Nov
Dec
Jan
Feb
Mar
Apr
Atrai Chainage 54,290 m
At Atrai Railway Bridge.
19.61
11.62
7.62
5.27
4.31
4.42
Sib-Barnai Chainage 49,450 m
at Chapai. Nawabganj
3.27
0.29
0.26
-
-
-

Impounding Reservoir 
Figure 8: Beel Joania 
In this situation where GW is not a sustainable source and SW seems inadequate to meet the demand, impounding reservoir of waters could be feasible. In wet season, huge amount of runoff occurs in this region. If water can be trapped here, this could loosen the demand pressure from GW sources. 





The north~eastern part of Tanore is comparatively low and surface runoff from Barind Tract is trapped initially at this depression. A retention pond in this region may be feasible to store the rainfall runoff from adjacent catchment. The catchment has the potential to conserve a huge amount of water in the depression. 
Figure 8: Digital Elevation map for Barind Region 
There is a low lands named ‘Beel Joania’ located east of Tanore. The areas of this Beel is approximately 1 km2. This area contains water round the year. There are rainfall stations at Tanore, Manda, Nachole. IWM and BUET conducted a study to carry out seepage and percolation in several locations in Barind region in 2005. This study has found following results. These findings will be used to calculate the infiltration loss. 

Table 2: Estimated Percolation Rates 
Location
Soil Type
Soil Texture
Upazila
Percolation
Rate
(mm/day)
Paba
Ganges
Silty loam
Paba, Puthia, Charghat, Bagha.
3.0
Baghmara
Old Ganges
Silty loam
Baghmara, Durgapur, Mohnapur, Shibganj (upper part), Bholahat, Atrai (Lower part).
3.0
Shibganj
New Ganges
Silty loam
Chapai Nawabganj, Shibganj (lower part).
4.0
Manda
Teesta
Silty clay
Badalgachi, Naogaon, Manda, Raninagar (western part).
2.0
Godagari
Lower Barind
Silty clay
Tanore, Godagari, Raninagar (eastern part), Atrai (upper part).
2.0
Niamatpur
Middle Barind
Clay loam
Porsha, Niamatpur, Nachole, Mahadebpur, Gomostapur.
2.0
Sapahar
Upper Barind
Silty clay loam
Sapahar, Patnitala, Dhamoirhat.
2.0

After analyzing 30 year data of rainfall, Average yearly net rainfall (after percolation) has been found 961 mm. It is observed that in dry season there is apparently no rainfall and percolation rate is higher. After forming a reservoir, some water will percolated into the ground. In that case, percolation loss would be a little higher. An average monthly rainfall is presented graphically below: 
Figure 9: Monthly average Effective Rainfall Distribution 
According to DEM, we can assume a reservoir of 4 km2 and adjacent catchment of 700 km2. Summary for water availability in wet season: 

Catchment Area: 700 km2 
Average yearly Rainfall: 961 mm 
Available Water: 672,700,000 m3 
Other losses (assumed): 50% 
Net Available Water: 336,350,000 m3 




Reference 
1. Banglapedia 
2. Surface Water Assessment report, GWM Project (DPHE), Institute of Water Modelling (IWM), 2011