Water Storage and Irrigation

Transcription

1 Annex 5 Water Storage and Irrigation Introduction The January 26, 2001 earthquake has caused widespread and severe damage to the water storage and irrigation infrastructure in Gujarat s Kutch and, to a lesser extent in Saurashtra region. In Kutch, 21 earthen dams have, to date, been identified as severely affected and require complete reconstruction, while 164 earthen dams have been identified to date as requiring major or moderate repairs and strengthening. (Such earthen dams are also sometimes referred to as "reservoir embankments," but the term earthen dam is more commonly used and will be used here). In Saurashtra 61 earthen dams have been identified to date as suffering moderate to minor damages, and requiring repair and rehabilitation. Some structures and linings in the canal networks, both in Kutch and Saurashtra regions, have also suffered damages, and will also require repairs/rehabilitation. Urgent addressing of the above works is critical. Twenty-one severely affected earthen dams would breach causing serious risk to life and property, if not either reconstructed or cut open ( so that the water is not stored ) before the onset of the July 2001 monsoon. A number of other earthen dams also present risks unless repaired and strengthened by July, All these dams are sources of supplies of rural and urban drinking water, industries and agriculture, and their full functioning by July 2001 or, latest, by July 2002 is a strategic priority. The damages are limited to earthen dams on medium and minor schemes, generally to those constructed before the 1970s with either no or lower seismic engineering design standards than the modern dams. More recently constructed dams, and dams for major schemes have not been affected. Consultations, Assessment Material and field visits This assessment is based on: (a) detailed working meetings with the Department of Water Resources (WRD), Government of Gujarat (GOG), (b) review by the Assessment Team of WRD s preliminary report, (c) consultation with the three inspection teams sent by the Central Water Commission (CWC), Government of India s apex Technical Organization under the Ministry of Water Resources, and (d) extensive field visits by the Assessment Team in company with the senior/project level officers of WRD, and a subsequent review meeting on February 19, 2001 by the Assessment Team with the Secretary, WRD, GOG, and the three Assessment Teams of the CWC led by Chief Engineer, Dam Safety Organization. The Assessment Team s site visits over five days (February 13-17, 2001) were to eight water storage/irrigation schemes in the worst earthquake affected Bhuj, Bhachau, Anjar, and Rapar Talukas of Kutch district, and five schemes in the moderately affected districts of Rajkot, Surendranagar and Jamnagar in the Saurashtra region. The schemes visited were: (a) Kutch district (seismic zone 5): Fategadh and Shivalakha (Rapar taluka), Ratia, Natharkui, Kaswati and Rundramati (Bhuj Taluka), Chang (Bhachau Taluka) and Tapar (Anjar Taluka); and (b) Saurashtra region (seismic zone 4): Machhu-II and Ghadodrohi (Rajkot district), Und-II (Jamnagar district) and Nimbhani, and Limbdi Bhogavo (Surendranagar district). Damage Assessment Mission Observations. The Assessment Team observed that, while all the above mentioned 8 earthen dams in the worst affected areas of the Kutch district have suffered severe damages (such as, complete collapse of some dams, very deep multiple cracking, crumbling and rupturing of earthen dam body, sloughing and settlement of slopes; and deep

2 crack formations on slopes associated with slippage s of boulder pitching, rendering the dams of these schemes absolutely unsafe and unfit for water storage); the damages in the storage dams of the 5 schemes in the Saurashtra region are generally of moderate to minor nature (such as minor cracks in short reaches of earthen embankments, slight settlements at the junctions of the earth dams and the spillways, small damages to the masonry wing walls and to the concrete pedestals under the spillway bridge girders etc.) and have not suffered any serious distress. Damages have also occurred in the distribution networks of all schemes visited, including damages to some canal structures and lining. Damage to Assets As per seismic zoning of India, Kutch region falls in the most vulnerable and earthquake-prone zone V. The epicenter of the earthquake being in the Kutch district, 12.5 kms. N-NE of Bhachau, the dams and appurtenant structures in this region have experienced the major impact. The severely affected dams visited have become nonfunctional due to widespread and diverse damages caused by the earthquake. No storage of water for irrigation/drinking water is possible till these dams are rehabilitated through reconstruction based on the revised upgraded designs conforming to the relevant Indian Standards applicable to the design of dams in various seismic zones. There are 20 medium and 165 minor irrigation dams/schemes in Kutch district. Besides the 8 dams visited, 13 more dams are reported to be likewise severely damaged requiring reconstruction. The balance 164 dams have also suffered moderate to major damages. In Saurashtra region, the range and types of damages caused by the earthquake in 61 schemes (44 medium and 17 minor) are of moderate to minor nature, and will require some repairs and strengthening. Besides the storage dams, the distribution networks of all the above schemes have also suffered moderate to minor damages. The total cost of the above damages is provisionally estimated to be about Rs. 186 crores ($40 million) (Table 1). Table 1: Effects of the disaster Total in Rs. Crores ($ million) Total with upgrade in Rs. Crores ($ millions) Reconstruction/Re pair period (years) Cost of asset replacement Public 186 (40) 419 (90) 18 months 2 years Private Rural 186 (40) 419 (90) Urban Sources: GOG, Assessment Team estimates

3 Based on the reassessment by GOG and the assessment team review, the revised cost of reconstruction and rehabilitation/strengthening to the latest earthquake resistant design standards is provisionally estimated to be anything up to Rs. 419 crores ($90 million). However, this figure is provisional and should be subjected to further scrutiny. Other Impacts In Kutch region, agriculture output in about 73,000 hectares (ha) of irrigated area will severely suffer, impacting the income and food security of about 365,000 rural population in 216 villages. In addition, drinking water supply in 2 towns and 26 villages covering a population of about 224,000 has also been affected. In Saurashtra region, agriculture output in about 181,000 ha of irrigated area will moderately suffer, impacting the income of about 1,800,000 rural population in 444 villages. Drinking water supply in 19 towns and 224 villages covering a population of about 5.9 million has also been affected. Further, as Kutch and Saurashtra regions are water scarce with the average annual rainfall ranging only from 25cm to45 cm, the population in these areas may face the added problem of migration of some people and cattle due to loss of assured sources of water supply on account of damages to the water storage/irrigation infrastructures. Though, it is difficult to quantify the other damages, agriculture output may drop significantly in the irrigated areas in Kutch and Saurashtra regions. Reconstruction Needs and Recovery Strategy Reconstruction Needs: As indicated in the table above, total reconstruction cost, including upgrading to modern seismic engineering standards, might be anything up to Rs. 418 crores ($90 million). This consists of the urgent short term needs before end June 2001, and the possible medium term need to end March 31, The aim is to start providing full irrigation and drinking water benefits by impounding the waters from the July 2002 monsoon. The break up is as under: Urgent short term need Rs crores ($15 million) Up to June 30,2001 Possible medium term need Rs crores ($75 million) July 2001-March 31,2003 Recovery Strategy: The critical safety and strategic nature of the reconstruction works will require a combination of parallel and sequenced actions on an urgent basis, which has been given in an Action Plan developed by the WRD. Summary details, divided by Immediate Actions, and Medium-term Actions are given below: Immediate Needs/Actions: (a) In schemes, where it is not possible/feasible to reconstruct the dams before the onset of July 2001 monsoon, appropriate cuts in the earthen dams are required to be made for the evacuation of flood flows.

4 (b) Urgent constitution of 2 Dam Safety Panels, one for Kutch, and one for Saurashtra and other regions. (c) Completion of the requisite investigations, soil sampling and testing to determine the relevant soil parameters to be adopted in the design of earth dams required to be reconstructed/strengthened to the upgraded standards. (d) Identification of the borrow areas of the construction material (bearing and casing soils etc.) to be used. (e) Inspection of all dams by WRD, and, as needed by OSP, to check for existent of any other damaged dams that have not yet been identified. (f) Completion of the designs of earth dam sections conforming to the latest relevant Indian Standards applicable for the reconstruction of dam embankments, in seismic zones, in Kutch region. (g) Immediate site visits of dam safety panels for inspection and finalization of the designs of earth dam embankment and the remedial measures for rectifying the various range of damages (h) Finalization of the cost estimates, bid documents, and initiate tendering processes for execution of works. (i) Keeping the earthmoving and compaction equipment in full readiness for undertaking reconstruction of three dams (Taper, Shivlakha, and Kasvati) departmentally. The activities (i) to (j) listed above may be taken up concurrently. The restoration measures which need to be completed by June 30, 2001 are included in this phase. Possible Medium Term Needs/Actions (a) Completion of other civil works necessary to secure the safety of the dams and also to derive planned benefits from these schemes latest by June 30, 2002 (i.e., before the monsoon of the year 2002)

5 (b) Completion of other balance works and the software activities by March 31, Implementation Arrangements The Water Resources Department will implement the reconstruction and remedial works through the Chief Engineers and Field Construction Circles. Whenever so needed, GOG will arrange additional construction staff through re-deployment. GOG has a well established, well staffed, and well equipped mechanical organization which is considered fully competent to undertake and complete the reconstruction of 3 dams critical for water supply in Kutch region in the immediate phase viz. by June 30, Other works of reconstruction, repairs, strengthening and restoration could be implemented through contracting and ideally, by June 30, GOG has a strong designs organization to undertake requisite design works. Necessary quality control and quality assurance arrangement will also be placed to ensure quality execution of works. Keeping in view the urgency and nature of works to be completed within a short time frame (some of the works before June 30, 2001, and the balance ideally in a period of about 18 months), fast-track procurement procedures should be considered. Nevertheless, these are very significant investments, and they should be given rapid but extremely careful scrutiny before decisions to proceed are taken.