Kenya - Additional Financing for the Water and Sanitation Services Improvement Project : environmental assessment (Vol. 3 of 14) : Feasibility study and master plan for developing new water sources for Nairobi and satellite towns

 E2905 v3 REPUBLIC OF KENYA MINISTRY OF WATER AND IRRIGATION ATHI WATER SERVICES BOARD (AWSB) FEASIBILITY STUDY AND MASTER PLAN FOR DEVELOPING NEW WATER SOURCES FOR NAIROBI AND SATELLITE TOWNS Preliminary EIA for the Selected Scenario: Nairobi Water Sources, Phases 1 & 2 Version 03 December 2011 in association with : MANGAT, I.B. PATEL & PARTNERS Egis Bceom International Contents in association with MIBP Contents Executive Summary....................................................................................................iv 1 Introduction...........................................................................................................1 1.1 Master Plan for New Water Sources for Nairobi and Satellite Towns....................... 1 1.2 Description of the Administrative, Policy and Regulatory Framework ..................... 2 1.3 World Bank Environmental and Social Safeguards Policies and Triggers ................ 9 1.4 Consultations............................................................................................................ 12 2 Study Area...........................................................................................................13 2.1 Geology.................................................................................................................... 13 2.2 Topography and Drainage........................................................................................ 13 2.3 Climate..................................................................................................................... 14 2.4 Groundwater Resources ........................................................................................... 15 3 Development of Groundwater Well Fields .........................................................16 3.1 Potential Groundwater Well Fields .......................................................................... 16 3.2 Scoping of Potential Impacts ................................................................................... 17 3.2.1 Preliminary Exploration ............................................................................................. 17 3.2.2 Development of New Well Fields and Increased Extraction from existing Well Fields .......................................................................................................................... 21 4 Development of the Northern Collector Tunnel, Phase 1 ...................................22 5 Downstream Reserve Flows................................................................................24 5.1 Environmental Flows ............................................................................................... 24 5.2 Environmental Flow Characteristics ........................................................................ 27 5.3 Options for Environmental Flow Release ................................................................ 36 5.4 Indicators of Hydrologic Alteration ......................................................................... 38 5.4.1 Range of Variability Approach................................................................................... 38 5.4.2 RVA Analysis............................................................................................................. 38 5.5 Compensation Flows................................................................................................ 42 5.6 Recommendations for Reserve Flow Release .......................................................... 44 5.7 Impacts from Abstraction of Flows.......................................................................... 46 5.8 Recommendations for Operating Rules ................................................................... 47 6 Cumulative Impacts ............................................................................................50 7 Upstream Catchment Areas.................................................................................55 7.1 Catchment Protection ............................................................................................... 55 7.2 Water Quality........................................................................................................... 57 7.3 Importance of Tea Cultivation ................................................................................. 58 8 Anticipated Impacts and Mitigation Measures....................................................60 8.1 Protected Areas and Endangered Species ................................................................ 60 8.2 Impacts from Construction....................................................................................... 62 8.2.1 Maragua Intake........................................................................................................... 62 8.2.2 Gikigie Intake ............................................................................................................. 63 8.2.3 Irati Intake .................................................................................................................. 65 8.2.4 Outlet Works .............................................................................................................. 66 8.2.5 Excavated Material from the Northern Collector Tunnel ........................................... 68 8.2.6 Transmission and Distribution Pipelines .................................................................... 69 8.3 Impacts from Operation ........................................................................................... 72 8.4 Impacts and Mitigation Measures ............................................................................ 73 8.5 Aquatic and Riparian Environments ........................................................................ 80 8.5.1 Impacts on Aquatic and Riparian Species .................................................................. 80 8.5.2 Impacts on Diseases ................................................................................................... 81 8.5.3 Interbasin Transfers .................................................................................................... 83 8.6 Analysis of Alternatives........................................................................................... 84 9 Environmental Monitoring Plan..........................................................................89 9.1 Draft Environment Management Plan...................................................................... 91 FEASIBILITY STUDY AND MASTER PLAN FOR DEVELOPING NEW WATER Page i SOURCES FOR NAIROBI AND SATELLITE TOWNS Preliminary EIA Version 03 Egis Bceom International List of Tables in association with MIBP List of Tables Table 4-1: Northern Collector Phase 1 Components.................................................................................................... 22 Table 5-1: Common Characteristics for each Flow Component for different disciplines ............................................ 27 Table 5-2: Environmental Influences of Different Flow Components ......................................................................... 29 Table 5-3: Characteristic Environmental Flow Components, Irati (RGS: 4BE6+4BE7, 1950-2010) .......................... 30 Table 5-4: Characteristic Environmental Flow Components for Gikigie (RGS: 4BE8, 1950-2010) ........................... 32 Table 5-5: Characteristic Environmental Flow Components for Maragua (RGS: 4BE9, 1950-2010) ......................... 34 Table 5-6: Characteristic Flows at Proposed Abstraction sites on Northern Collector ................................................ 38 Table 5-7: Summary of Assessments of Hydrologic Alteration on flow rates for the proposed intake sites for Northern Collector Phase 1, comparing the release of 2 x Q95 Reserve Flows with Reserve Flows generated by variable abstraction and release procedures. ..................................................................................................... 41 3 Table 5-8: Estimates for Required Minimum Downstream Reserve Flows (m /s), NC Phase 1 ............................. 43 Table 5-9: Districts directly impacted by modified downstream flows, showing proportion of households using streams and estimated requirements for household use ......................................................................................... 43 Table 6-1: Average flows into Masinga Reservoir (m3/sec), and potential changes following diversion of water to the Northern Collector Phase 1.......................................................................................................................... 53 Table 8-1: Impacts related to pipeline construction and operation............................................................................... 70 Table 8-2: Impacts due to Construction of weirs, intake structures and tunnels .......................................................... 74 Table 8-3: Impacts due to Operation of Weirs ............................................................................................................. 75 Table 8-4: Yield of Existing Water Sources ................................................................................................................ 84 Table 8-5: Potential New Water Sources Identified..................................................................................................... 85 Table 8-6: Water Demand Forecast: Nairobi City ....................................................................................................... 85 Table 9-1: Pre-Construction Phase Information Requirements.................................................................................... 93 Table 9-2: Environmental, Safety and Health Issues during Construction Phase......................................................... 95 Table 9-3: Environmental Issues during Operational Phase....................................................................................... 100 List of Figures Figure 3-1. Possible location (red circle) of a 35,000 m3/day well-field in Kiunyu sector, near the Thika River. ...... 17 Figure 3-2. Possible location (red circle) of a 30,000 m3/day well-field in the north of Kiambu - NW of Ruiru area. ....................................................................................................................................................................... 17 Figure 5-1: Example of flows during a relatively dry period - Irati River 1975-1976 (RGS 4BE6 and 4BE7 combined flows m3/sec) ........................................................................................................................................ 26 Figure 5-2: Example of flows during a relatively wet period - Irati River 1997 - 1998 (RGS 4BE6 and 4BE7 combined flows) .................................................................................................................................................... 27 Figure 5-3: Environmental Flow Components in Irati River (RGS: 4BE6 plus 4BE7), and flows recorded 1982 – 1985, illustrating Environmental Flow Components. ......................................................................................... 30 Figure 5-4: Annual Frequency of flows in each of the five EFC categories for Irati River (RGS: 4BE6 plus 4BE7), 1970-2010.................................................................................................................................................. 31 Figure 5-5: Average annual low flows (Base Flow) and extreme low flow (Subsistence Flow) in Irati River (RGS: 4BE6 plus 4BE7), (m3/sec) 1970-2010....................................................................................................... 31 Figure 5-6: Environmental Flow Components in Gikigie River (RGS: 4BE8), and flows recorded 1982 – 1985, illustrating Environmental Flow Components ....................................................................................................... 32 Figure 5-7: Environmental Flow Components in Gikigie River (RGS: 4BE8), and flows recorded 1996 – 1999, illustrating Environmental Flow Components, including large floods................................................................... 33 Figure 5-8: Frequency of flows in the EFC categories for Gikigie River (RGS: 4BE8), 1970-2010 ........................... 33 FEASIBILITY STUDY AND MASTER PLAN FOR DEVELOPING NEW WATER Page ii SOURCES FOR NAIROBI AND SATELLITE TOWNS Preliminary EIA Version 03 Egis Bceom International List of Tables in association with MIBP Figure 5-9: Average annual low flows (Base Flow) and extreme low flow (Subsistence Flow) in Gikigie River (RGS: 4BE8), (m3/sec) 1970-2010 Note: Compare average values for extreme low flows with the Q95 flow value of 0.052 m3/sec............................................................................................................................................. 33 Figure 5-10: Environmental Flow Components in Maragua River (RGS: 4BE9), and flows recorded 1984 – 1986, illustrating Environmental Flow Components ............................................................................................. 34 Figure 5-11: Frequency of flows in EFC categories for Maragua River (RGS: 4BE9), 1970-2010............................. 35 Figure 5-12: Average annual low flows (Base Flow) and extreme low flow (Subsistence Flow) in Maragua River (RGS: 4BE9), (m3/sec) 1970-2010............................................................................................................... 35 Figure 5-13: Irati intake: Flow Duration Curves. Natural Flows (green) and Downstream Release using 2xQ95 (red).............................................................................................................................................. 36 Figure 5-14: Example of downstream flows following abstraction at proposed Irati Weir (2007-2008). A: Natural Flows and B: downstream flows after abstraction using (i) the recommended thresholds for variable extraction and (ii) release of 2xQ95 after abstraction (m3/sec). ............................................................................. 37 Figure 5-15: Frequency of EFC category High Flow Pulses before and after abstraction at Irati Weir, illustrating the difference between (A) Variable Release and (B) 2xQ95 for delivery of downstream Reserve Flows. .................................................................................................................................................................... 40 Figure 5-16: Summary of Assessments of Hydrologic Alteration on downstream flows at proposed intake sites: A). Variable abstraction and release, and B). 2 x Q95 for Reserve Flows ............................................................. 41 Figure 5-17: Locations in upper parts of Muranga North and South Districts (2009 National Census) through which Maragua, Gikigie and Irati Rivers flow....................................................................................................... 44 Figure 6-1: Flows at Maragua RGS:4BE1, 2008-2010 (m3/sec), illustrating characteristic seasonal patterns of flow with occasional periods of small floods and large floods (extreme low flows were not recorded during this period)............................................................................................................................................................. 51 Figure 6-2: Flow Duration Curves at Maragua RGS:4BE1. Natural flows (green). Change following abstraction for Northern Collector and release of 2xQ95 (red). ............................................................................................... 51 Figure 6-3: Natural Flows at Maragua RGS:4BE1 during 1991 (m3/sec), illustrating a period with extreme low flow........................................................................................................................................................................ 52 Figure 6-4: Flows at Maragua RGS:4BE1 (1950-2010). Differences between the average monthly Natural flows and Modified flows with 2xQ95 released at Northern Collector intakes ............................................................... 52 Figure 6-5: Trends in international crude oil prices: Daily Brent Crude 2000-2011 (US$ per barrel), with best-fit trend line (power curve, R2=0.801) extended to forecast till year 2017..................................................... 54 Figure 7-1: Northern Collector tunnel (including Phase 1 and Phase 2) and Thika Reservoir: Showing Protected Forest areas, National Park land, and rivers connected to the project .................................................... 56 Figure 7-2: Land use adjacent to site of proposed Maragua Intake Weir, illustrating Smallholder Tea as dominant land use.................................................................................................................................................. 57 Figure 8-1. Proposed site for the Maragua Intake Weir ............................................................................................... 63 Figure 8-2. Proposed site for the Gikigie Intake Weir ................................................................................................. 64 Figure 8-3. Location of the Proposed Gikigie Weir ..................................................................................................... 65 Figure 8-4. Location of proposed Irati Weir and Intake Shaft: .................................................................................... 66 Figure 8-5. Proposed site for Outlet Works above Thika Reservoir, showing riparian vegetation and surrounding tea plantation. .................................................................................................................................... 67 Annex Annex 1: Indicators of Hydrologic Alteration Annex 2: Proceedings of Stakeholders Workshop on 30th August 2011 held at Intercontinental Hotel, Nairobi. FEASIBILITY STUDY AND MASTER PLAN FOR DEVELOPING NEW WATER Page iii SOURCES FOR NAIROBI AND SATELLITE TOWNS Preliminary EIA Version 03 Egis Bceom International List of Tables in association with MIBP Executive Summary The Government of Kenya has received a credit from International Development Association (IDA) and the Agence Française de Développement (AFD), and intends to apply part of the proceeds for Consulting Services for Improving Water Security: Feasibility Study and Master Plan for Nairobi and Satellite Towns. The Water Sources Options Review, August 2011, compared six potential development scenarios on the basis of a range of technical and natural resources, economic, environmental, and social criteria. The development of bulk water sources to supply Nairobi and 13 satellite towns will impact on the general water resources balance in the region as a whole. The chosen development scenario, considered as the priority strategy to meet the 2017 water demand for Nairobi, includes two initial phases for which potential environmental impacts are assessed. These are: • Phase 1: Groundwater development in Kiunyu area (2014) then in Ruiru area (2015); • Phase 2: Northern Collector Tunnel Phase I from Maragua, Gikigie and Irati Rivers to Thika reservoir (2016) This report focuses on the potential impacts relating to Phase 1 and Phase 2. Initial investment options for Phases 1 and 2 involve the development of two well fields at Kiunyu and Ruiru to supply groundwater (with an estimated total yield of 64,800 m3/d) and development of the Northern Collector Phase 1 (with an estimated yield of 138,240 m3/d). These developments are expected to increase Nairobi water supply by 50% over current supply levels by 2017. The availability of potential groundwater resources was presented in the Review of Groundwater Resources, June 2011. A program of exploratory drilling is required in order to locate suitable high yielding formations and to give precise estimation of the well-fields’ potential and to confirm the availability and suitability of this resource, significant use of this groundwater resource as part of the Nairobi water supply is expected. In the absence of more detailed plans, a full environmental assessment is not currently feasible. However, a scoping of potential impacts from the potential development of these well fields and associated distribution pipelines is presented. Potential impacts include: 1. Changes in groundwater contribution to base flows in rivers, and reduction in local water supplies available from springs and dug wells. 2. Degradation of aquifers. 3. Clearance of vegetation as a result of site establishment and associated impacts on agricultural land. 4. Impacts from drilling activities themselves, including noise, and accidental spillage. Important mitigation measures include the installation of an increased network of river gauges and recording stations in order to fully cover the potentially impacted areas. Regular, daily monitoring and reporting of these river gauges will be necessary. At times when reduced base flows are considered to have occurred, or are likely, and where these fall below accepted Reserve Flow limits, it will be necessary to supply an increased flow from upstream resources in order to compensate for the reduced flow and to ensure FEASIBILITY STUDY AND MASTER PLAN FOR DEVELOPING NEW WATER Page iv SOURCES FOR NAIROBI AND SATELLITE TOWNS Preliminary EIA Version 03 Egis Bceom International List of Tables in association with MIBP adequate downstream flows (environmental flows and compensation flows). Springs and wells in the areas within the geological strata affected by the proposed groundwater well fields also need to be identified and the yields monitored. Alternative, piped water supplies may need to be provided in cases where these water sources are impacted by reduced groundwater levels resulting from abstraction. Longer term impacts will subsequently result from the operation of each of the well sites together with associated transmission and distribution pipelines. This will include: • Compensation for loss of land. • Compensation for loss of agricultural production and livelihoods. • Operation of the pipeline wayleave in private land. • Impacts resulting from potential pipeline leakage. Phase 2 of the selected scenario for development of water sources for Nairobi includes the development of the Northern Collector Tunnel Phase I. This will enable the abstraction and diversion of water from Maragua, Gikigie and Irati Rivers to Thika reservoir. Implementation is planned by 2016. The main environmental and socioeconomic impacts resulting from the Northern Collector Tunnel Phase 1 will be related to the diversion of water, and the resulting reduction in downstream flows in these rivers. This requires the assessment of the required downstream Reserve Flows, including both environmental flows and compensation flows. Such impacts are expected to be long-term. Additional impacts are related to the construction of the facilities themselves. However, these are expected to be local-level and relatively short-term impacts. Downstream Reserve Flows are described, including compensation flows and the characteristics of environmental flows. Options for environmental flow release are outlined, including (i) the release of 2xQ95 Reserve Flows and (ii) the adoption of an alternative strategy that depends on the volume of incoming flow, with greater proportions being abstracted from higher flows together with the specification of a "hands off" flow below which no abstraction is allowed. The details of variable abstraction rates can be adapted at individual intake sites to cater for the needs of all users. Results of flow modelling show that abstractions will reduce the frequency of middle-level and high-level flows and increase the frequency of low-level flows. The general absence of high flow pulses, small floods and large floods, associated with release of 2xQ95 Reserve Flows will result in inevitable long-term changes to downstream riverine and riparian environments. Operational procedures will need to be established so that, under periods with naturally low flows (e.g. extreme low flows), sufficient flows are allocated to: a) Cater for downstream demands from communities, households, agriculture (crops and livestock), and commercial or industrial requirements, b) Provide environmental flows of sufficient quantity to prevent critical decline of downstream aquatic environments, c) Ensure the maintenance of water quality (including the requirements related to sewage treatment and disposal), and d) Provide some flow for Nairobi water supplies whilst taking account of available storage in reservoirs. Rationing of water to all consumers may need to be considered under such circumstances. FEASIBILITY STUDY AND MASTER PLAN FOR DEVELOPING NEW WATER Page v SOURCES FOR NAIROBI AND SATELLITE TOWNS Preliminary EIA Version 03 Egis Bceom International List of Tables in association with MIBP An important recommendation is that all river flows must be monitored and reported on a regular daily basis both above and below each of the weirs and intake structures, as well as at sites downstream. Information on flows will then be available to form the basis for day-to-day operational management decisions. Regular monitoring and updating of downstream water abstraction and use will need to be carried out. This includes, for example, the use of water by households and communities, or for use as irrigation supplies and commercial/industrial use. This should include both currently licensed and unlicensed abstractions. This information will need to be fed into regular operating procedures in order to optimise the use of available water resources and continue to provide environmental flows capable of maintaining downstream environments and critical environmental services. Cumulative impacts are considered, and are expected to include the following primary considerations: • Reduced flows as a result of diversion of a majority of the flows originating from the Aberdares at Irati, Gikigie and Maragua intakes to the Northern Collector, resulting in: • Reduction in the flow reaching Masinga Reservoir of 3.17% on an annual basis, and therefore a reduced flow available for hydroelectric power generation. • Some short periods or single days with potentially zero flow (0.33% of daily flows). These periods can be mitigated by the release of higher flows from the Northern Collector intake sites over selected periods in order to prevent unacceptable low flows downstream. • Less flow available for use by future agricultural activities in selected downstream areas (irrigation) that can be expected to be in demand in order to provide some of the additional food required by the increasing population of Nairobi. Catchment protection is an important component of the overall management of water resources. Impacts related to catchment protection in the Irati, Gikigie and Maragua catchments are considered to be manageable issues with no negative impacts. Major parts of the catchments of the proposed Northern Collector abstraction sites are included within the protected areas of the Aberdares, including the Aberdare National Park and neighbouring Aberdare Forest Reserve. Significant parts of the catchments are therefore considered to be under a “high protection" status. Outside of the protected areas, land cover of managed land is predominantly tea plantation. The deep roots and ground cover provided by tea results in relatively good soil and water conservation. Downstream of the intake weirs it is also recommended that regular land management and control measures will be required for catchment protection, in particular in order to reduce the risks of soil erosion. Where possible this should be combined with local on-farm water harvesting measures and agricultural practices such as Conservation Tillage. The Maragua, Gikigie and Irati Rivers each provide riparian vegetation along their length. Over this stretch of river no specific important ecosystems are identified with the exception of this riparian vegetation that provides an important natural corridor. Reduced flows will have an overall negative impact on the riparian vegetation cover, with expected long-term effects including reduced habitats, degraded stream bank stability, and potential changes in the depth of the water table. Combined with expected increase in clearance for agricultural activities, the long-term changes to riparian vegetation are expected to have a negative impact on the species diversity and populations of many bird, small mammal and other wildlife species using these resources. As a result, population numbers of some bird species are expected to decline downstream of the intake structures. Impacts are expected to reduce in intensity further downstream as other FEASIBILITY STUDY AND MASTER PLAN FOR DEVELOPING NEW WATER Page vi SOURCES FOR NAIROBI AND SATELLITE TOWNS Preliminary EIA Version 03 Egis Bceom International List of Tables in association with MIBP tributaries merge with the main rivers and the effective catchment area increases, providing some seasonal hydrological changes, including small floods and large floods. Potential negative impacts that can be expected from construction of the proposed intakes at Irati, Gikigie and Maragua, together with the construction of the Northern Collector Tunnel include: a) Land acquisition and loss of cultivated areas, especially smallholder tea, in areas adjacent to the Intake Sites. b) Soil erosion resulting from site preparation and construction activities, including the construction of weirs, tunnels and pipelines. c) Change in local topography during site preparation/grading. d) Pollution from machinery and construction activities. e) Construction of access roads, temporary settlement and workmen’s camps, and permanent offices and settlement required to maintain and run each of the weirs. f) Disposal of rock and other material excavated from the Northern Collector Tunnel and access shafts. g) Pollution from machinery and construction activities, including accidental spillage. h) Possible impacts on hydrogeology as a result of tunnelling. Construction activities will result in significant volumes of excavated material derived from the rock excavated from the tunnels. No areas for “spoil