Empirical Field Study On Variation Of Arsenic

In hand, pump Tube wells During Operation Of Irrigation Wells

Final Report December 2001

DISASTER FORUM (Partner Organization of OXFAM)

5/8 Sir Syed Ahamaed Road Block-A, Mohammadpur

Dhaka-1207 Tel: 8128146

Fax: 088-02-8128146 E-mail: df@bangla.net

Prepared by :

Abu Shahjalal Azad

Assisted by :

Sumaya Noor Shirin Sultana

Acknowledge

Disaster Forum gratefully acknowledges the financial contribution made by UNICEF. Bangladesh towards the implementation of the study. It also deeply appreciates the support and cooperation it received from Mr. Shahidul Islam, Member, Sayesta Union Partishad, Ward No. 7 of Singair Upazill, District Manikganj. DPHE Singair Upazilla. The owners and caretakers of all handtubewells and irrigation wells and others who directly and indirectly extended their corporation to conduct the study as well as to write the report.

Table of Contents Abstract

1. Introduction 2. Main Features of the Study 3. Implementation

3.1 Identification of Study Area 3.2 Preparation of Physical Map of the Study Area 3.3 Collection and Analysis of Water Samples 3.4 Daily Logging of Operation of the Irrigation Wells

4. Analysis 4.1 Variation of arsenic in tubewells 4.2 Relationship between arsenic concentration in handtubewells and horizontal distance

from the irrigation wells 4.3 Relationship between handtubewell depth and arsenic concentration 4.4 Arsenic variation in wet season

5. Conclusion 6. Recommendation\ 7. References

Abstract: Arsenic is considered associated with buried sediments and under reducing condition it is released into groundwater. Prior to 1970 when millions of people were drinking tubewell water for decades from more than 200,000 hand pump tubewells, there was no known arsenic related problem. This implies, though arsenic was in ground water, its entry into hand pump tubewells was insignificant. But after liberation in 1971, large-scale installation of hand pump tubewells in both public and private sector began. Today there are about 4 million hand pump tubewells in the country. Though this figure is appalling, it is believed that these wells do not significantly influence groundwater movement, hence no or limited role in entry of arsenic into themselves. The other most significant development that took place since liberation was ground water based irrigation to boost food production. The growth of irrigation wells between early 1970s and late 1990s has been revolutionary. The number of irrigation tubewells grew from few hundreds to about 800,000 during this period. These wells operate round the clock during dry season (January-June) abstracting water at a high rate accelerating ground water movement. It is believed that this accelerated movement of groundwater is one of the causes of entry of arsenic into hand pump tubewells. To test this hypothesis the subject study in an existing field situation in Niltek village, Singair, was undertaken. The study area consists of two irrigation wells surrounded by eight hand pump tubewells. Arsenic was measured monthly from each well during January to November 2001 to note the variation over the period. At the same time, daily operating time of the irrigation wells was recorded. No other data such as water level, bore log, soil analysis etc. was collected. But depths and distances of the hand pump tubewells from the irrigation wells were measured. The most significant finding of the study is that considerable variation of arsenic in each well was observed, often exceeding safe limit, during the entire period under study with peaks during dry season as well as wet season. Towards the end of dry season when the irrigation wells completed most of its total operating hours, the arsenic concentrations in hand, pump tubewells were independent of their horizontal distances from the irrigation wells implying no relationship with the horizontal movement of ground water. But some inverse correlation between the depths of the hand pumps tubewells and arsenic concentration has been observed. This implies significance of vertical component of the ground water flow transporting arsenic vertically down from the upper layer of soil, which is believed to be the main source of arsenic underground. WHO in its guideline stated that average content of arsenic in earth crust is 2 mg/kg. In Samta, South Western Bangladesh, the upper layer of soil contains from 0.7 to 23.0 mg/kg. of arsenic rising as high as 46.5 to 261.5 mg/kg. in peaty samples. In the wet season, also when irrigation wells were not operative, higher arsenic concentration was observed in the hand pump tubewells. This is probably caused by mixing of groundwater with upper soil due to rise of water level in wet season. The other reason could be that arsenic in shallow layers of soil were dissolved by rainwater and infiltrated underground to reach the groundwater table. These findings except the observed variation in arsenic concentration are only presumptive to be studied further more scientifically for confirmation. However, this is clearly indicated that testing of tubewells for screening purpose should be carried out in April-May and October-November, because, arsenic concentration in hand tubewells are higher in these periods of the year.

1. Introduction Arsenic in ground water was detected in early 1990s in Bangladesh. The scale of the problem, its causes and possible future change are not known. Several studies have been carried out by various agencies since then, but the exact cause and the magnitude of the problems are yet to be fully understood. It is considered to be of natural and geological origin. Natural process of sedimentation and sediment transport create variation in the arsenic problem within the Bengal Basin; once the sediment are buried, they rapidly become strong reducing, and natural geochemical process of desorption and dissolution release arsenic from the sediments in the ground water. Local variation in the rate of groundwater movement due to the location of rivers and variation in topography or type of sediment (clay, silt or sand) probably account for much of the local variation. On the other hand ground water based irrigation was not considered to be the major causes of the ground water arsenic problem but further study on its possible long term impact was recommended by the British Geological Survey (BGS)m in one of its st udy report published in March, 2000. The BGS report said that the hand pump tube wells are unlikely to have a major effect on ground water flow, but irrigation wells with their large volumes of abstraction will tend to draw from ground-water recharge in preference to the rivers and thereby may change the local hydraulic gradients in the system markedly. However, it suggested that the time for arsenic to travel to shallow-hand-tubewells is estimated to be of the order of 560 years whereas the time to travel to deep-hand-tubewells is estimated to be in excess of 200 years. Burt this suggestion on length of time seems to be not entirely correct because of the following facts: • In 1970, prior to the national programme of installation of hand pump tube-wells, there were already

more than 200,000 hand pump tubewells in the country providing drinking water to millions of people of Bangladesh. At the same time there were a few irrigation well in the country. Surprisingly at that time, there was not known problem of arsenic sis among the drinkers of tube-well water. It does point to subsequent development of external causes that either accelerated release of arsenic from sediment to ground water, or accelerated ground water movement with spread of arsenic or both.

• From 1972, large-scale hand pump tubewell installation programmes began and from about the

same time to increase food production, installation of irrigation wells under Bangladesh Agriculture Development Corporation (BADC) started in a modest scale in phases. Later from mid 1980s to accelerate food production installation of wells through BADC stopped and the responsibility was developed onto private sector, more specifically to individuals. Because of high demand, mushroom growth of irrigation wells took place without any consideration to zone of influence, safe abstraction rate etc. As a result, about 8-lakh irrigation well have been installed so far and these well operate round the clock throughout the entire dry season when the high yielding paddy needs continuous watering. Table-1 shows annual growth of irrigation well from 1982-83 to 1999-2000. From this table it will be observed that the number of shallow tubewell was 93,100 in 1982/83, which shot up to 757,100 in 1999-2000. The growth of deep tubewell during the same period was rather low marking an increase of 11,300 from 13,800 to 25,100. The longer the dry spell, the longer is the operating time. During the past several years drought or near drought condition was almost a recurring annual phenomenon. Consequently, the irrigation wells remained operational for

prolonged period each year. It is quite likely that due to prolonged operation at a very high rate of abstraction, ground water movement became faster than normally estimated. Hence, faster movement of arsenic along with ground water, and the time to access to hand pump tube wells is reduced particularly when it is too extensive.

In view of the above, it is assumed that while arsenic is of natural and geological origin, accelerated groundwater movement caused by over pumping of irrigation wells has influenced the movement at a faster rate. A long-term study will hopefully be carried out by expert agencies in due course to determine the impact of irrigation. The present empirical study is however a modest endeavour to see the change if any, in arsenic concentration of hand pump tubewells in real life condition when the irrigation wells in operation. A 11-month-long study from January 201o to November 2001 was undertaken to see the changes in arsenic concentration of eight hand pump tubewells during operation period, and in pre & post operational condition of the 2 irrigation wells. This final report is intended to present the findings of the study.

Table-1

Operational Irrigation tubewell by Season, 1982/83 to 1999/2000

Irrigation Annual operating equipment (‘000 units) STW DTW

1982/83 93.1 13.8 1983/84 120.3 15.5 1984/85 147.0 16.9 1985/86 146.9 17.9 1986/87 160.3 18.7 1997/88 188.7 20.3 1988/89 235.9 22.4 1989/90 260.0 22.6 1990/91 270.3 21.5 1991/92 309.3 25.5 1992/93 348.9 25.7 1993/94 359.2 24.4 1994/95 488.9 26.7 1995/96 576.2 27.3 1996/97 629.8 25.2 1997/98 664.7 25.3 1998/99 736.1 26.7 1999/00 757.1 25.1

Source: National Minor Irrigation Census (NMIC). 1999/2000 Prepared by NMIDP with the assistance of Department of Agricultural Extension (DAE), Dhaka January.

2. Main Features of the Study 2.1 Identification of a proper study area comprising active irrigation wells surrounded by a number of

hand pump tubewells at different distance and depths in arsenic affected location near Dhaka. 2.2 Preparation of physical map of the intervention area showing the irrigation wells and the hand pump

wells to be studied./ the depths and distance of the hand pump well from the irrigation wells to be indicated in the map.

2.3 Measuring monthly total arsenic of all study wells including the irrigation well with AAS with first measurement taken prior to commencement operation of the irrigation well for the season.

2.4 Daily recording operation time of the irrigation pumps in logbook. 2.5 Preparation of a report based on all data collected.

A work plan (annex-1) was prepared in the light of the above req1uirements and was followed. 3. Implementation 3.1 Identification Study Area:

The process of identifying a proper study area began in November 2000/ Following field visits and with active support from DPHE Singair Upazilla and Mr Md Shahidul Islam, Member of Union Parishad, ward no. 7 of Sayesta Union of Singair Upalilla an area within Niltek village was selected for the study. Mr Md Shahidul Islam provided all necessary help and ensured cooperation from the community, particularly the owners or caretakers of the study wells. The study area consists of an agricultural land stretching North-South with inhabited areas located on East and West sides. The selected irrigation wells are in the agricultural land and the shallow hand pump wells are in the inhabited areas.

3.2 Preparation of he Physical Map:

A map of the study area, Fig. 1 was prepared. The map shows the distance of the hand pump tubewells from the irrigation wells as well as the depths of all wells.

Map of the Study Area

TW.NO. TYPE OF TW DEPTH OWNER/CARETAKER 1-1 Irrigation 90’ Badsha Pramanik 1-2 Irrigation 90’ Aftab Bepari S-1 Irrigation 55’ Mujibur Bepari S-2 Shallow HP 42’ Naimuddin Bepari S-3 Ditto 57’ Badsha Pramanik S-4 Ditto 57’ Nasir Uddin S-5 Ditto 53.5’ Raij Uddin S-6 Ditto 53’ Ahejuddin S-7 Ditto 153’ Wahab Master S-8 Ditto 54’ Abdul Aziz

3.3 Collection and Analysis of Water Samples:

From 2 irrigation wells, 11 water samples were collected during February-November, 2001. Irrigation wells were not operated after April because of heavy early monsoon rain. Rainfall data of Dhaka Brahmaputra Basin since 1981 is presented at Table-2. It is seen from the table that highest rainfall occurred during April-June 2001 compared to the rainfall of the table that highest rainfall occurred during April-June 2001 compared to the rainfall of the previous corresponding periods.

Table-2

Rainfall Data of Dhaka (Brahmaputra Basin) From 1981-2001)

Year Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 1981 10 42 108 244 411 325 356 187 320 82 09 35 1982 00 15 81 104 154 514 140 346 258 146 54 00 1983 18 63 138 318 348 298 181 408 322 253 00 18 1984 13 01 07 124 707 635 690 309 477 58 00 00 1985 08 01 195 176 300 399 262 317 306 79 00 10 1986 06 00 23 231 191 308 450 171 687 237 172 03 1987 03 00 33 230 109 316 526 462 363 104 07 33 1988 00 45 74 282 517 579 255 164 196 213 153 03 1989 00 32 00 85 228 319 347 59 305 240 00 12 1990 00 36 151 154 202 229 567 227 247 181 103 06 1991 27 08 46 53 529 320 318 345 692 392 14 106 1992 01 47 00 25 153 132 386 182 158 83 02 00 1993 00 52 88 113 556 500 421 432 417 217 19 00 1994 13 54 115 201 254 266 153 246 169 55 14 00 1995 08 31 00 88 264 237 354 361 205 91 112 00 1996 00 21 54 199 208 343 257 361 244 257 00 00 1997 02 07 82 133 151 249 549 230 440 30 01 22 1998 49 04 83 178 405 89 521 552 246 100 83 00 1999 00 00 00 21 428 348 553 282 361 368 13 00 2000 13 44 172 189 608 165 197 359 46 248 00 00 2001 00 72 110 460 1754 2091 1431 920 1222 774 145 00 Source: Bangladesh Met office:

From the eight hands, pump tubewells. 110 water samples were collected during January –November 2001. All 121 (11+110) water samples were analyzed for total arsenic in Intronics laboratory using AAS./ Hydride Generation method of analysis was employed by the laboratory. Result of analysis is prepared in Table-3.

Table-3 Arsenic Study Wells Expressed in Part Per Billion

Tubewell No.

Arsenic in PPB. Date-wise 11-1-01 8-2-01 17-2-01 1-3-01 31-3-01 15-4-01 29-4-01 17-5-01 31-5-01 1-7-01 29-7-01 28-8-01 26-9-01 31-10-01 28-11-01

11 - * - 43.9 114.0 11.5 - - - - 109.0 92.1 57.1 - 94.0 12 - 88.0 - 7.65 99.9 2067 - - - - - - - - - S1 44.7 39.5 - * 28.6 75.9 84.4 117.0 71.2 50.8 448.1 43.5 31.3 66.2 52.7 S2 33.9 50.7 - 19.9 37.3 90.2 105.0 106.4 60.6 77.6 59.1 41.9 30.2 64.5 54.6 S3 103.5 * 50.70 46.5 62.5 60.3 77.2 * 88.2 87.3 83.4 66.1 43.9 115.0 125.2 S4 20.0 35.9 - 36.6 41.9 36.7 38.9 41.5 77.0 54.5 59.5 60.1 50.6 7606 69.6 S5 50.7 36.6 - 24.4 33.8 22.8 53.3 79.0 40.1 93.0 60.9 58.0 47.5 86.2 75.2 S6 34.8 60.1 - 22.9 22.4 11.0 61.0 96.2 87.8 78.5 58.5 55.9 36.3 65.2 71.2 S7 63.4 80.4 - 106.0 67.8 28.4 42.4 58.2 70.4 72.4 91.8 82.7 61.5 125.0 114.4 S8 52.8 136.3 - 27.1 61.1 17.3 115.0 85.4 68.5 76.3 77.2 64.2 50.5 97.1 91.5 Note : (1) 1-1 and 1-2 are irrigation wells. 1-1 started operation from 22 January and 1-2 from 6 February 2001 (2) S-1 to S-8 are hand pump tubewells. * Water samples could not be collected as the pumps were not in operation.

First samples from the 8 hand pump tubewells were collected in January 2001 prior to the commencement of seasonal operation of the irrigation wells. Irrigation well I-1 commenced operation from January 22 and I-2 from February 2001. The study intended to note variation in arsenic concentration of the hand pump tubewells in question throughout the whole study period. Particularly during the full blast operation of the irrigation wells, which is supposed to be March-June? Unfortunately, for the study, but fortunately for the farmers, early monsoon rain in sufficient volume caused the irrigation wells to cease operation in the most critical period. As a result, one of the objectives of the study will remain partially unmet. It may be noted from Table-3 that the frequency of collection of water samples from the hand pump tubewells was increased in April to May anticipating full operation of the irrigation wells.

3.4 Daily Logging of Operation of the Irrigation Wells Logbooks with appropriate formats were provided to owners of the irrigation wells for recording

daily operating time for each spell of operation with specific starting and ending time. Accordingly, they recorded the operating period of their respective wells. It is found from the logbook that I-1 operated from 6 am to 11 am and from 4 pm to 10 am everyday throughout the entire operating period. I-2 also maintained the same operating period from February 6 to mid March. In the second half of March, it was operated for longer period. Total monthly operating period of each irrigation well is presented in Table-4. It will be seen from this table that total hours of operation decreased in April while it was supposed to increase. This was due to early monsoon rain in substantial volume. Irrigation well 1-1 was re-operated in August and September 2001 for a very short period.

Table-4

Hours of Operation of Irrigation Wells Irrigation on well

Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Total hours

I-1 130 364 403 312 - - - 26 1 - - 1236 I-2 00 260 431 330 - - - - - - - 1021 Note: I-1 operated from January 22 to April 26, 2001 and then again in August and September for a

very short period. I-2 operated from February 6 to April 30, 2001.

4. Analysis 4.1 Variation of arsenic in tubewells The variation of arsenic concentration in each hand tubewell has been quite significant during the study period, January-November, 2001. The following table shows the range of variation.

Table-5

Rang e of Variation Arsenic in Hand Tubewells

Hand tubewells ID No Lowest Arsenic Concentration in PPB

Highest Arsenic Concentration in PPB

S-1 28.6 117.0 S-2 19.9 106.4 S-3 43.9 125.2 S-4 20.0 77.0 S-5 22.8 93.0 S-6 11.0 96.2 S-7 28.4 114.4 S-8 17.3 136.0

If lowest values of arsenic concentrate ion of all the hand tubewells are considered they all meet the criteria of a safe well, but if the highest values are taken, none meets the criteria. But the most critical finding is that arsenic concentration in each well change continuously within short span of time. The arsenic concentration of the irrigation wells also varied significantly. The ranges of variation in 1-1 and 1-2 in PPB are 11.5-114.0 and 2.67-99.90 respectively. Variation curves of all 10 wells are presented in 10 figures from fig.2 to fig. 11. Dotted lines below the curves show the time of operation of the nearest irrigation well.

4.2 Relationship Between Arsenic Concentrations in Hand Tubewells and Horizontal Distance From Irrigation Well. Assuming accelerated ground water flow during the dry season caused by 3-4 months of operation of irrigation wells, arsenic concentration in hand, tubewells at different distances from nearest irrigation wells have been compared. The comparison has been presented in Table-6.

Table-6

Hand Tubewell ID No. Distance from the nearest irrigation well in feet

Arsenic in PPB in end April

S-1 200 84.4 S-2 550 105.0 S-3 479 77.2 S-4 350 38.9 S-5 542 53.0 S-6 689 61.0 S-7 707 42.4 S-8 740 115.0

From the above table no consistent relationship between arsenic concentration in hand tubewell and their horizontal distance from irrigation well can be observed. As cumulative operating hours of both irrigation wells culminated in end April, end April data have been taken to compare arsenic variation in the hand tubewells caused by the irrigation wells, if any. 4.3 Relationship between hand tubewell depth and arsenic concentration Please refer to fig.-12. This compares arsenic concentration in end April 2001 in hand tubewells of different depths. Assuming maximum impact of irrigation wells, if any, on arsenic variation taken place in end April, the end April data have been taken to compare arsenic concentration of different hand tubewells with their depths. It will be observed that hand tubewells between 42 and 57 feet depths contain arsenic between 39 and 115 PPB and the tubewells between 90 and 153 feet depths contain arsenic between 2.67 and 42.4 PPB. (As hand tubewell S-7 is deeper than the nearest irrigation well, apparently there should be no influence of irrigation well on it). This phenomenon tends to indicate that the vertical component of the ground water flow accelerated by pumping of irrigation wells stimulates faster downward movement of water, hence quicker entry of arsenic in greater quantity into the tubewells of lower depths than those with greater depths. This is quite likely, as the main source of arsenic is the upper soil. According to WHO guidelines for drinking water quality the average arsenic concentration in the earth’s crust is about 2 mg./kg. A research-group which conducted research in Samta village in Western Bangladesh found high arsenic content in the first aquitard (upper muddy layer), ranging from 3.0 to 261.5 mg./kg. and even higher content from 46.5 to 261.5 mg/kg. in peatgy samples within the layer. On the other hand, arsenic content in upper most muddy layer, upper most sandy layer and upper sandy layer was relatively low, ranging from 0.7 to 23.0 mg/kg.

In the (Niltek) study village, however, no soil sample analysis was done to determine neither the source of arsenic, nor any bore log to determine location and thickness of different types of soil was conducted. 4.4 Arsenic variation in Wet Season In the wet season also when irrigation wells were not operative, higher arsenic concentration was observed in the hand pump tubewells. This is probably caused by mixing of ground water with upper soil due to rise of water level in wet season. The other reason could be that arsenic in shallow soil layers were dissolved by rainwater and infiltrated underground to reach the groundwater table. 5. Conclusion Variation of arsenic in hand tubewells occur continually and it has been sufficiently indicated that the irrigation wells impacts on groundwater flow, and its vertical component causes downward movement of arsenic along with water from upper layers of soil. However, a thorough study taking into groundwater flow, groundwater level, lithology, soil analysis etc. into consideration will confirm the findings. 6. Recommendation: Hand tubwell testing for arsenic for screening purpose should be carried out in April-May and October-November to be on the safe side. The reason for such a recommendation is that arsenic in handtubewells tends to be at its peaks during these periods of the year.

7. References 7.1. Groundwater Studies for Arsenic Contamination in Bangladesh: Draft Final Report – Summary:

British Geological Survey et al. 7.2 Arsenic Contamination in Groundwater and Hydro geological Background in Samta Village:

Western Bangladesh, July 2000 by Sub-group for Arsenic Contamination et al. 7.3 Guidelines for Drinking Water Quality, Vol-2: Health Criteria and Other Supporting Information,

WHO.

Annex-1 Empirical Field Study to Find Variation of Arsenic in Hand pump Tubewells during Operation of Irrigation wells

Sl. No.

Description of Activities Dec. 2000

Jan. 2001

Feb. 2001

Mar. 2001

Apr. 2001

May 2001

June 2001

July. 2001

Aug. 2001

Sept. 2001

Oct. 2001

Nov. 2001

Dec. 2001

1 Identification of the study area and selection of sample wells (irrigation and handpump tubewells) 2 Mapping of the study area through proper survey 3 Collection of water samples from the selected irrigation and hand pump tubewells 4 Analysis water samples by AAS for arsenic 5 Logging daily operation time of irrigation wells 6 Preparation and submission of an interim report 7 Preparation and submission of final report