Climate Change Risk and Adaptation Assessment for Irrigation in Southern Viet Nam

Water Efficiency Improvement in Drought-Affected Provinces

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• Publisher: Asian Development Bank
• Year: 2020
• Print ISBN: 9789292625078
• eBook ISBN: 9789292625085
• Topic: Biological Sciences
• Subtopic: Global Warming & Climate Change
• Index: Biological Sciences

This publication presents findings from a climate change risk and adaptation assessment in southern Viet Nam as part of the Water Efficiency Improvement in Drought-Affected Provinces (WEIDAP) project supported by the Asian Development Bank. It highlights new developments and key lessons on climate risk assessment that may be applied to the project design and monitoring as well as the implementation of climate adaptation measures. The WEIDAP project was developed in response to the drought that affected southern Viet Nam in 2015–2016. It focused on irrigation modernization and the integration of climate-resilient agricultural and efficient on-farm water management practices.

1 Introduction

This report deals with the climate risk and adaptation assessment (CRA)¹ of the Water Efficiency Improvement in Drought-Affected Provinces (WEIDAP) project of the Asian Development Bank (ADB) in Viet Nam. The CRA was developed in collaboration with the technical assistance (TA) team, and initial findings were discussed leading up to and during the project’s midterm review. This report gives an overview of climate risks and vulnerabilities to inform the detailed design of the project and the implementation and monitoring of identified climate adaptation measures. It also highlights lessons learned during the CRA and signposts relevant references and resources in each main section.

The WEIDAP project was prompted specifically by the severe El Niño–Southern Oscillation (ENSO)– induced drought of 2015–2016 (Stockdale, Balmaseda, and Ferranti 2017), which affected Viet Nam’s South Central Coast and Central Highlands regions, and more broadly by Viet Nam’s national climate change strategy, which seeks to enhance food security and water resource security in the face of future climate uncertainty. The project is designed to promote climate-resilient agricultural practices through a transformational program of irrigation modernization, including (i) strengthening irrigation management to improve climate resilience, (ii) modernizing irrigation infrastructure, and (iii) supporting efficient on-farm water management practices. Eight irrigation systems in the five drought-affected provinces of Binh Thuan, Dak Lak, Dak Nong, Khanh Hoa, and Ninh Thuan will be modernized (ADB 2018b). Irrigation modernization will make the provinces better able to manage climate variability, improve water productivity in agriculture, and increase farm incomes by promoting the cultivation of high-value crops including coffee, pepper, grape, apple, dragon fruit, and mango (ADB 2018b).

The general findings of the WEIDAP CRA are relevant to all eight subprojects. Further detailed analysis, including more detailed water resource modeling and economic analysis, was completed for two subprojects at the Song Mong, Ba Bau and Trung Tam reservoirs. These case studies illustrate the sensitivity of the proposed schemes to future climate change scenarios, the potential impact on return on investment, and the relative benefits of the schemes as outlined and some potential further refinements.

This CRA report is structured as follows:

• Section 1 gives background information about the WEIDAP project, ADB’s CRA requirements, and the project methodology.

• Section 2 is a summary of current climate conditions in the Central Highlands and southeast Viet Nam, with a focus on natural variations. It also calls attention to the most relevant climate risks.

• Section 3 contains information about future climate change, including the climate change scenarios projected by the Ministry of Natural Resources and Environment (MONRE) in 2016 and three complementary future scenarios developed for the sensitivity testing of WEIDAP project design.

• Section 4 presents summary information about the vulnerability of farmers exposed to climate change, based on a household survey done under the TA and on published data.

• Section 5 assesses in greater detail the main climate risks related to water supply and demand, the frequency of floods and droughts, and other potential impact on agricultural production.

• Section 6 contains an adaptation assessment using the climate scenarios and risk assessment to stress-test two case studies under the baseline (no-project) case and with the WEIDAP project.

• Section 7 presents overall conclusions and recommendations for the WEIDAP project and also for the development of CRAs.

Project Background

The WEIDAP project is aimed at improving water productivity in irrigated agriculture in five drought-affected provinces of the South Central Coast and Central Highland regions of Viet Nam (ADB 2018b). It is focused on eight subprojects in Binh Thuan, Dak Lak, Dak Nong, Khanh Hoa, and Ninh Thuan provinces. Inefficient rice irrigation schemes will be replaced with modernized systems using pipes (pressurized and gravity), upgraded canals, and impounding weirs designed for irrigating high-value crops, such as mango, coffee, pepper, and dragon fruit.

The project was developed in response to the prolonged drought in 2015–2016 and to meet the anticipated challenges of climate change. The drought in Viet Nam, which was driven by strong El Niño conditions, affected around 60,000 hectares of agricultural land in the Central Highlands, including the main area of coffee production, as well as 20%–30% of the areas growing rubber, pepper, cashew, and tea (ADB 2017a).

Climate variability and climate change are closely linked. Under many future scenarios, floods and droughts are projected to occur with greater frequency, alongside increases in average temperature and changes in average seasonal rainfall (Box 1; sections 2 and 3). The project activities can therefore be viewed as climate change adaptation to ensure reliable water supply for high-value crops under normal to moderate drought conditions.²

Box 1: The WEIDAP Project as a Climate Change Adaptation Project

The climate in the Central Highlands and South Central regions of Viet Nam is highly variable. During the southwest monsoon in 2015, there was 40%–70% less rainfall than normal in the five selected drought-affected provinces. Temperatures in the Central Highlands have already risen (Katzfey, McGregor, and Suppiah 2014; MONRE 2016), increasing in turn the demand for water.

Many future scenarios project changes in annual rainfall, but also with increased variability. This indicates the risk of less reliable supplies and an increase in the frequency of extreme droughts. In this context, the WEIDAP project can be regarded as a climate change adaptation project in response to the drought conditions and in anticipation of more variable climate conditions in the future.

Climate change and sea-level scenarios for Viet Nam released by the government in 2016 (MONRE 2016) indicated increases in average annual rainfall by the 2050s. However, year-to-year variations in seasonal rainfall are more important for water efficiency and irrigation projects. Even small changes in average conditions may lead to an increase in both floods and droughts.

The WEIDAP project includes proposed climate adaptation activities for the agricultural water sector. In the chart below, all the activities with check marks are already included in the project. Yellow flags indicate potential for further linked adaptation projects, for example, in drought planning, and red flags mark important considerations in detailed engineering design.

C1 = component 1; C2 = component 2; C3 = component 3; IWRP = Institute of Water Resources Planning, Viet Nam; MONRE = Ministry of Natural Resources and Environment, Viet Nam; TA = technical assistance; WEAT = water-efficient application technology; WEIDAP = Water Efficiency Improvement in Drought-Affected Provinces project.

Sources: Katzfey, J. J, J. L. McGregor, and R. Suppiah. 2014. High-Resolution Climate Projections for Vietnam: Technical Report. Australia: Commonwealth Scientific and Industrial Research Organisation (CSIRO); Ministry of Natural Resources and Environment (MONRE), Viet Nam. 2016. Climate Change and Sea Level Rise Scenarios for Vietnam: Summary for Policy Makers. Ha Noi; ADB TA team.

Box 1 presents a rationale for regarding the WEIDAP project as a climate change adaptation project for the agricultural water sector, both in response to the drought of 2015–2016 and in anticipation of future climate change. It includes a summary of activities under the WEIDAP project and its major components—institutional strengthening, modernization of irrigation systems, and improvement of on-farm water management. Box 1 also highlights the potential for aligned pro-poor projects that may be eligible for further climate financing.

Building further flexibility into the outline designs for irrigation systems to take climate change into account is difficult because these designs are already well developed (e.g., in terms of pipe sizes, anticipated irrigation command areas, flow rates). However, the way the schemes operate is more flexible and could respond to changes in hydrological regime and water availability (pump scheduling, pump allocation, etc.). Component 1 (institutional strengthening) and component 3 (on-farm water management) (section 7) can also incorporate refinements and additional activities.

Due diligence of the ADB investment project indicated risks of extreme floods and droughts, particularly in the first few years after implementation, climate change risks, and a wide range of effects of socioeconomic factors, such as the following:

• water management and allocation,

• licensing,

• water pricing,

• access to finance,

• labor cost, and

• market price.

Climate change could variously affect crop water demand, crop growth and yield, the availability of water for irrigation, and the frequency of floods, droughts, and heat waves. The CRA of the WEIDAP project pertained mainly to the reliability of water supply and the frequency and magnitude of future droughts. However, other climate risks were considered in the development of the scenarios presented in sections 3 and 5.

ADB Approach to Climate Risk and Adaptation Assessment

ADB’s Climate Risk Management (CRM) Framework requires early screening of projects for potential climate risks. More detailed risk assessment work is needed for projects with a high- or medium-risk rating.

According to ADB guidance (2015a), “a detailed climate risk and adaptation assessment is carried out for projects classified as medium or high risk during project preparation. The assessment aims to quantify risks and identify adaptation options that can be integrated into the project design. The level of technical rigor of the assessment depends on the project complexity and availability of climate data and information for the project area. It can range from a simple desk analysis to a complex assessment based on custom climate projections to enable a more detailed assessment.”

After a more detailed assessment of project risks and vulnerabilities, including economic analysis, additional activities may be classified as climate change adaptations.

Climate Risk and Adaptation Assessment Methodology

Although ADB provides some guidance on the scope of CRA reports,³ there is no fixed methodology, as the scope of work must reflect the type of investment, the timing of the CRA versus other activities in the project preparation phase, and the size of the project.

In this study, the CRA was developed alongside the TA activities. Figure 1 outlines the main methodological steps. The assessment team first had to complete a rapid review of the WEIDAP inception report and available literature to gain a better understanding of the key drivers of climate variability in the Central Highlands and South Central Coast regions of Viet Nam.

Figure 1: Main Steps in the ADB Climate Risk Management System and Methodology Used in the Water Efficiency Improvement in Drought-Affected Provinces Climate Risk and Adaptation Assessment

ADB = Asian Development Bank, WEI = water efficiency improvement, WEIDAP = Water Efficiency Improvement in Drought-Affected Provinces.

Source: ADB technical assistance team

The methodology included climate risk assessment and adaptation assessment in the ADB CRM Framework

The entire project is a response to water scarcity and drought conditions in 2015–2016. Therefore, drought vulnerability is well understood. In addition, outline designs, including the size of command areas to be served by improved irrigation, were well developed. This meant that fast-tracking to a slightly more top–down CRA suited this particular project and its timescales.

The methodology was based primarily on a literature review, consultation with the international and national TA experts, and case-study assessment. It involved the following steps:

• Identifying current climate risks through a review of the inception report and research literature, and an understanding of baseline climatology and particularly the impact of the drought.

• Reviewing climate change projections, inc...

Table of contents

• Front Cover
• Title Page
• Copyright
• Contents
• Tables, Figures, and Boxes
• Acknowledgments
• Abbreviations
• Executive Summary
• 1. Introduction
• 2. Climate in Viet Nam’s Central Highlands and South Central Coast Regions
• 3. Review of Available Climate Change Projections and Scenarios
• 4. Vulnerability to Future Climate and Socioeconomic Changes
• 5. Climate Risks
• 6. Adaptation Assessment
• 7. Conclusions and Recommendations
• Appendixes
• Bibliography
• Footnotes
• Back Cover