Ground Water Information Booklet Tirap District, Arunachal Pradesh

Home , Changlang district, Deomali, Khonsa, Tirap district

Technical Report Series: D No: 10/2011-12

Central Ground Water Board North Eastern Region Ministry of Water Resources Guwahati

June 2011

TIRAP DISTRICT AT A GLANCE

Sl ITEMS Statistics No 1. GENERAL INFORMATION i) Geographical area (sq. km) 2362 ii) Administrative Divisions No. of Sub-divisions 4 No. of Block 6 No. of Villages 167 iii) Population (As per 2011 Census) 111997 iv) Average Annual Rainfall (mm) 3478.5 2. GEOMORPHOLOGY Major physiographic units Lesser Himalayan zone, Intermontane valleys, Foothill zones Major Drainages Namsang, Tissa, Chetun, Tirap 3. LAND USE (sq. km) a) Forest area 1025.62 b) Net area sown 133.42 c) Cultivable area 179.29 4. MAJOR SOIL TYPES Loamy, fine loamy, coarse loamy, silty, sandy and clayey 5. AREA UNDER PRINCIPAL CROPS, ha (2010-11) Rice-5625, Millet-4775, Maize-2755, Oil seeds -820 6. IRRIGATION BY DIFFERENT SOURCES (Area and number of Structures) Dug wells/ Tube wells/ Tanks/ Ponds/ Canals Nil Other sources Surface flow 129 Nos. Surface water lift 1 No. Net irrigated area (ham) 228 Gross irrigated area (ham) 228 7. NUMBER OF GROUND WATER MONITORING WELLS OF CGWB (As on 31-3-2013) No of Dug Wells 03 No of Piezometers Nil

8. PREDOMINENT GEOLOGICAL FORMATIONS Disang, Barail, Tipam and Alluvial Formation 9. HYDROGEOLOGY Major Water bearing formation Alluvium, Tipam Sandstone Pre- monsoon Depth to water level during 2011 Post- monsoon Depth to water level during 2011 10. GROUND WATER EXPLORATION BY CGWB (As on 31-03-2013) No. of wells drilled (EW, OW, PZ, SH, Total) EW: 2 Nos. Depth Range (m) 108 to 113 Discharge (liters per minute) 33 to 700 Drawdown (m) 14 to 22 Transmissivity (m2/day) 132 11. GROUND WATER QUALITY Presence of Chemical constituents more than permissible limit Fe, 07 to 2 mg/lit Type of water Soft to moderately hard 12. DYNAMIC GROUND WATER RESOURCES (2009) in ham Annual Replenish able Ground Water Resources 11000.17 Net Ground Water Availability 9900.16 Net annual Ground Water Draft 2.80 Projected Demand for Domestic and Industrial Uses up to 108.5 2025 Stage of Ground Water Development 0.028% 13 AWARNESS AND TRAINNING ACTIVITY Mass Awareness Programme organized Nil Date Place No. of Participants 14. EFFORTS OF ARTIFICIAL RECHARGE & Nil RAINWATER HARVESTING Projects completed by CGWB (No & Amount spent) Projects under technical guidance of CGWB 15. GROUND WATER CONTROL AND REGULATION Nil Number of OE Blocks No of Critical Blocks No of blocks notified 16. Major Ground Water Issues and Problems High concentration of iron (>2ppm) in some areas.

1. INTRODUCTION

The mountainous Tirap district of Arunachal Pradesh has a geographical area of 2362 sq k.m. It is located within N. Latitudes 26˚38΄ to 27˚47΄ and E. Longitude 95˚40΄. The district lies in the southern side of the Brahmaputra River and in the southern part of the state. Northern part of the district is bounded by Sibsagar district of Assam, eastern side by Changlang district of Arunachal Pradesh, western part by Mon district of Nagaland and southern side by Myanmar. Khonsa, the headquarters of Tirap district is approachable from both Tinsukia (120km) and Dibrugarh (125km) town of Assam. The district is divided into 4 administrative sub-divisions which are further divided into 6 blocks (Khonsa, Deomali, Lazu, Niausa, Pongchau Wakka, Kanubari). Total population of the district is 111,997 as per Census 2011. The decadal growth rate (2001-2011) is 11.63% and population density is 47 per sq.km.

DRAINAGE

Tirap district is a part of the Tirap basin. Namsung is the major river of the district. It flows into Buri Dihing forming a natural boundary of some length between the district of Tirap and the state of Assam. Other important rivers of the district are Tissa, Chetum, Tirat, Dirok, Chatjo and Borap. Drainage pattern is sub-dendritic to sub- angular.

AGRICULTURE AND IRRIGATION

Agriculture is the mainstay of the people of Tirap district. All the cultivators stick to their traditional Jhum cultivation. There is no major irrigation projects in the district, except a few number of minor irrigation schemes. Amongst minor irrigation schemes Surface flow and Surface water lift are available. There is no ground water structure for irrigation. As per Agricultural Census 2010-11 net irrigated area of the district is 228 ha while gross irrigated area is also 228 ham. For this 129 no. surface water lift is used.

PREVIOUS STUDIES

Sh. J. K Verma, CGWB, NER first carried out a short term water supply investigation of Senua, 45km. from Khonsa for a proposed medical plantation farm in 1977. Sh. Verma was also entrusted to carry out first approximate ground water resource evaluation in Kanubari area of this district under CGWB exploratory programme. Sh. U. Gogoi, Scientist B, CGWB, NER attempted a detailed hydrogeological survey of the district during FSP 1985-86.

2. RAINFALL AND CLIMATE

The climate is predominantly cold, wet and highly humid. The area falls under heavy rainfall belt and annual average rainfall is 3478.5 mm. Monsoon generally starts in May /June and lasts till September, but winter rains are also considerable. The periods February – March and October – November may be considered as pre- monsoon and post-monsoon periods respectively.

3. PHYSIOGRAPHY, GEOMORPHOLOGY AND SOIL TYPES

PHYSIOGRAPHY

Physiographically the district can be divided into three main units which are as follows: a) The foothill zone, comprising undulating plains. b) The lesser Himalayan zone rising from the foothill zone, comprising a rugged mountainous and forested terrain, rising to a maximum attitude of 200m above M.S.L. c) Intermontane valleys with conspicuous terraces and older terrace deposits.

GEOMORPHOLOGY

The area has three distinct hydrogeomorphic units: i) Denudostructural hills: Occupy 90% of the area comprising Barail and Disang formations. Lithologically both the formations comprise shales, compact sandstones and siltstones. This unit represents a high runoff zone and has little importance from ground water development point of view. ii) Linear ridges: Exposures of Tipam sand stone group in the form of linear ridges are found in the north-western part of the district. This hydrogeomorphic unit comprises sanstone, shales and clay and represents a good source for ground water. iii) Valleys: Alluvium of the river Namsang in the north-western part of the district occurs as valleys. This hydrogeomorphic unit is also of importance from ground water development point of view.

SOILS

The soil developed on low altitudinal hills ranges with intermittent narrow valleys are loamy, fine loamy and clayey. Soils in upper piedmonts areas are loamy- skeletal or coarse-loamy in texture. Soils on undulating upland and gently sloping plain are fine/ fine-loamy/ coarse loamy or coarse-silty in texture. The soils developed in recent and active flood plain are coarse silty in texture. Soils on channel bars are sandy in texture. Soils are strongly to moderately acidic in reaction (pH 4.3-5.6). however, the soils of flood plain area are slightly acidic to mildly alkaline (pH 5.5 to 8.4).

4. GROUND WATER SCENARIO

HYDROGEOLOGY

The water bearing formations of Tirap district can be divided into two groups. a) Unconsolidated formation: This covers Alluvium zone, a linear stretch in NE- SW direction along Deomali area bordering Assam. The aquifer consists of fine sand, silt and boulders. Ground water occurs under unconfined condition in this formation. The unconfined aquifer exists down to a depth of 12 to 15 m bgl. The depth of ground water level varies from 4 to 6m bgl.

b) Semi-consolidated formation: Amongst the semi-consolidated formations only Tipam sandstone bears some significance. This formation consists of thick gritty ferruginous sandstone and clay. In this formation ground water under unconfined condition does not extend beyond 15 m bgl and depth of water level varies from 3-4 m below ground level. In deeper depths ground water occurs under semi-confined to confined conditions.

It is observed that shales belong to Disang and Barail Groups are of less important for ground water exploitation. Intermontane valleys present in this area are very small in extent, i.e. about 1 sq. km only. The valleys are consists of shales, compact sandstone and siltstone. At present no ground water structure is present in these valleys but there is scope for ground water development in the valleys.

SPRINGS

Ground water in the form of springs plays a vital role for rural water supply of this district like in other districts of this hilly state of Arunachal Pradesh. It is observed that fractures are the main controlling elements in the occurrence and distribution of the springs. Hydrogeomorphological map of the district is shown in plate 1.

GROUND WATER EXPLORATION

To know the characteristics of deeper aquifer two exploratory wells were constructed. The wells were constructed within 105m bgl. Discharge of the wells varies from 33 to 700 lpm and drawdown varies from 14 to 22 m.

5. GROUND WATER RESOURCES

The quantification of d namic ground water resource of the district has een estimated ased on methodolog recommended E 97. Because of the aucit of block / circle wise hydrological data, resource of the district as a hole has been estimated. An annual replenishable ground water resource of the district is 11000.17 ham. Net ground water availability of the district is 9900.16ham while net ground water draft for all uses is 2.80 ham. Projected demand for domestic and industrial uses upto 2025 is 108.50 ham. Ground Water Availability for future irrigation is 9788.86 ham. Stage of ground water development is 0.028% and thus the district can be categorized as safe.

6. GROUND WATER QUALITY

The chemical analysis of ground water samples collected from springs show that water is suitable for drinking, domestic and irrigation purposes. The general range of different chemical constituents is given in table 1.

Table 1: General range of chemical constituents in Tirap district

Chemical constituents Range PH 6.1 to 7.9 EC (micromhos/cm) 38 to 198 Carbonate (mg/lit) 18 to 128 Chloride (mg/lit) 4 to 21 Hardness as CaCO3 (mg/lit) 14.1 to 86 Calcium (mg/lit) 4 to 18 Magnesium (mg/lit) 1 to 10 Iron (mg/lit) .7 to >2

pH value of 6.1 found in Deomali area, whereas permissible limit pH value in drinking water is between 6.5 to 8 (BIS). EC values less than 130 micromhos / cm at 25˚ indicating ver low mineralisation. The hardness values of 14 to 86 mg/lit indicate that the water soft to moderately hard. Though in most of the water samples Fe is concentration is within permissible limit but, in two springs Fe content is found to be 2 mg/lit and not fit for drinking as well as for any household purpose.

7. GROUND WATER MANAGEMENT STRATEGY

GROUND WATER DEVELOPMENT

From the point of ground water development perspective, the boundary zone of Assam and Tirap district of Arunachal Pradesh with an area of 1.5 x 40 km is having some significance. The area extends from Dirok gate in the north to Kanubari in the east, passing through Deomali and Hukanjuri. In this area construction of dug wells and two deep tube wells is feasible.

WATER CONSERVATION AND ARTIFICIAL RECHARGE

Ground water development in the district is negligible. PHED, Govt. of Arunachal Pradesh is supplying water by tapping surface or spring water sources and is almost sufficient for the district. Therefore, artificial recharge is not required at present. However, roof top rain water harvesting may be promoted.

8.0 GROUND WATER RELATED ISSUES AND PROBLEM

High concentration of iron (>2ppm) both in springs as well as in tube well (Kanubari area) are present. Other than iron, no such problem has yet been identified or reported from this district. State department (PHED) tried to construct one tube well H.S. school, Kanubari by DTH with ODEX facility rig but after 50m depth due to presence of sticky clay drilling remained unsuccessful.

9.0 RECOMMENDATIONS

b) In the belt bordering Assam, ground water occurs under unconfined condition. The unconfined aquifer does not extend beyond 15 m bgl. The aquifer consists of thick gritty ferruginous sandstone with little clay. CGWB has constructed 2 successful deep tube wells in the area.

Construction of large diameter dug well down to a depth of 15 m (maximum) is feasible. In Kanubari township and Deomali area construction of deep tube well is feasible. Rotary rig is recommended for drilling in this area. c) Excluding the foot hill part bordering Assam, rest of the area of the district is not much feasible for ground water extraction. But, detailed geophysical survey in the valley areas are needed to know about the sub-surfaces condition as well as trial borehole in few selected sites based on geophysical survey, may be carried out. d) Springs plays an important role for rural water supply. Excluding the springs having high iron content (as noticed as per chemical analysis), rest may be utilized for rural water supply. It is also observed that most of the springs discharge dwindles, sometimes to a meager trickle during lean season. On the other hand during monsoon period, over flowing of water makes it muddy and unfit for drinking. To cope with these problems, construction of seepage tanks and filtration plants, wherever possible, need to be taken up. e) As the district is receiving high rainfall (2512 mm) and it lasts for eight to nine months of a year. Therefore, rooftop rainwater harvesting may be taken up.