Control

The B arind has in the past been considered as having a low potential for ground w ater developm ent, and has been described as not suitable for deep tube well (DTW ) developm ent and o f lim ited potential for shallow tube w ell (STW ) developm ent (U N /B W D B, 1983; Klinski, 1979; M PO, 1990). T he first large scale ground w ater assessm ent and developm ent project for the area, the R ajshahi Tube w ell Project, was undertaken by the Bangladesh A gricultural D evelopm ent C orporation (BA DC) in early 1980s. The project was abandoned after initial appraisal concluded there was only lim ited potential for D TW developm ent (U N /B W D B , 1983). In contrast, the suitability o f part o f the area for large scale ground w ater developm ent was established in a pilot scale project (A saduzzam an, 1982). A fter long debate, the Rajshahi Tube well Project was resurrected by the B A D C and re-nam ed as B arind

Integrated A rea D evelopm ent Project (BIA DP) with an initial aim of sinking 3000 deep tube w ells for irrigation in the 15 designated thana o f greater Rajshahi district. Each irrigation D TW has a capacity o f 90 1/s (7258 mVd) discharge and is intended for use over 4 months o f the dry season. The project from its inception created m uch debate am ong the environm ental scientists about the sustainability o f the w ater resource and vulnerability o f the environm ent due to this large w ithdraw al. The project is presently m anaged by the Barind M ultipurpose D evelopm ent A uthority (BM DA). There are currently about 5000 irrigation boreholes installed across the B arind and more are being drilled in the continuing program m e. In addition to these boreholes, a large num ber o f low capacity boreholes also operate in the area. The exact num ber o f these boreholes is not precisely known.

6.3.ii M o des o f A b stra c tio n

Surface w ater has always been the easily available source o f w ater to all hum an civilisation as is dem onstrated by the presence o f the all ancient civilisation along m ajor rivers. Surface w ater is very easy to collect for dom estic purposes. Canals are excavated to allow gravity flow to the irrigated land. W hen gravity flow is not possible, w ater is lifted either m anually by buckets or dons or m echanically by using low lift pum ps (LLP). LLPs are located along river the rivers and large bils\ in some cases they are used to lift w ater from large ponds or deep kharies. T he coverage given by surface w ater depends on the nature o f the source and type and capacity o f the lifting modes. One o f the largest surface w ater irrigation schem es in the area provides irrigation to 1214 hectres (300 acres) o f land w here w ater is collected from the river M ahananda.

W ith the advancem ent of the hum an civilisation com es the question o f quality rather than quantity and surface waters are always vulnerable to pollution. An alternate and purer source o f w ater is ground w ater abstracted from springs or dug wells. G round w ater has been abstracted in the area from very beginning o f human settlem ent in the area. The m ost early form o f abstraction is the dugw ell - m anually excavated 1 m to 2 m diam eter wells. Dug wells are used to exploit shallow ground w ater on the Barind. M ost o f these wells are shallow up to 20 m deep, w ith exception o f som e up to 30 m deep. A lthough m ost dug wells are used for drinking w ater supply, some also provide irrigation to a very lim ited area. W ater is abstracted from these wells m anually by using a pulley and bucket.

The next stage o f developm ent in the history o f ground w ater abstraction in the area was introduced in early 1960s by the developm ent o f 0.06 m diam eter boreholes, locally know n as hand tube wells (HTW ). These boreholes w ere developed for drinking w ater supply. They are com m only 30 to 40 m deep and exploit sand lenses within the clay. A bstraction by these bores are very small (norm ally < 1 1/s).

Then cam e the age o f large scale irrigation w hich requires large capacity boreholes. The early irrigation boreholes w ere the Shallow Tube W ells (STW ) - defined not by depth but by capacity o f the pum p and diam eter o f the discharge pipe. These boreholes are pum ped by lim ited capacity suction pum ps, w ith a pum ping lift o f six m etres and a m axim um discharge is 0.5 cusec (15 1/s or 1300 mVd). O ne such borehole can cater for the irrigation dem and o f an area up to 60 hectres (15 acres).

W ith the increasing dem and for irrigation w ater these pum ps becam e insufficient to supply the required quantity o f water. M anually O perated Shallow Tube wells for Irrigation (M O STI) are also developed in the area. M O STIs are low capacity

bore holes and capable of providing irrigation for up to one acre o f land.

The increasing dem and lead to the developm ent o f larger capacity boreholes - locally called the Deep Tube W ells (DTW ). The D TW s are also defined by their capacity and the diam eter o f the discharge main rather than depth. A standard DTW has a discharge capacity o f 3 cusec (90 1/s or 7777 mVd) and 0.36 m discharge pipe (Plate 6.1.A). They are operated by subm ersible pum ps w ith different pum ping heads as required. One such borehole can fulfil the irrigation w ater dem and o f 400 hectres (100 acres).

On account o f draw dow n produced by the high capacity irrigation boreholes the H TW s and STW s w ith their lim ited lifting capacity are falling into disuse. To overcom e this, many HTW s have been replaced by deep set hand pum ps. To overcom e the problem o f low lifting head o f the STW s, the farmers invented a technique o f placing the pum p in a shallow dug pit (Plate 6.1.B). Pits up to depth o f 3 to 5 m have been observed all over the study area. These STW s are called the D eepset Shallow Tube W ells (DSTW ). Fig 6.19 shows the different m odes o f w ater abstraction in the area.