Strengthening sub-basin agricultural water management in Asia through remote sensing and water accounting
Author: Dr Adam Lilicrap
The “Green Revolution” saw vast amounts of investment in irrigated agriculture which helped reduced poverty and malnutrition in many developing countries. The legacy however is that in many parts of Asia water resources in basins are fully exploited with competition for water between the different sectors; domestic, industry, energy, agriculture and the environment. Agriculture is still seen as an important economic driver to reduce poverty as well as maintain food security. Though, agriculture is often the largest consumer of water and to meet competing Sustainable Development Goals requires good data as well as good governance.
Decisions are being made, throughout Southeast Asia, about water usage at irrigation and farm scales with little understanding of the effects at the broader subbasin or basin scale. The current irrigation and water management practices resulting in overuse and declining water quality, mainly from agricultural contaminants (pesticides and nutrients) are threatening the sustainability of the water resource and communities depending on it.
The sustainable management of water resources at basin and sub-basin scales requires good management and regulation. Some of the management Interventions to improve water efficiencies and productivity to reduce water usage by agriculture have had the opposite effect with farmers due higher water availability increasing irrigated areas or cropping intensity resulting in higher water usage. Additionally, so called ‘inefficiencies’ such as leaking irrigation canals often resulted return flows that recycled water and were used elsewhere in the basin. The increased ‘efficiency’ meant water was no longer available to downstream users. To properly understand the impacts and correctly target management interventions an understanding of stocks, flows and uses of water are needed at broader sub-basin to basin scale. This is known as water accounting and is required for better management the resource base. Water Accounting is based on developing water balances for the area of interest, at different points in time to understand trends in water usage. This requires data that is not always available. Additionally, to properly manage water freed up from targeted interventions requires good governance.
The cost, and the know-how, to install as well as operate hydrological monitoring equipment, especially for groundwater can be excessive. Even if hydrological data is being collected it may be unavailable to the people making decisions as they could be in different government departments resulting in the lack of detailed and reliable data to develop water balances for water accounting purposes. At transnational and larger basin scales, water accounting tools are being developed and used working with big data and applying remote sensing and earth observation data products. However, the possibility for remote sensing data and associated products to assist decision makers with water management at sub-basin scales is not known. Another potential use of this data could be to ‘follow the water’ and better target management interventions, including understanding any potential off-site effects the interventions may have.
This ACIAR funded research project aims to investigate and test the usefulness of remote sensing in gap-filling hydrological data for water accounting, to aid agricultural water management at sub-basin scales in low/middle income countries. It will also identify existing and emerging remote sensing data products that can provide hydrological and other datasets relevant to agricultural water management.
A key component of the research design is early and repeated engagement with stakeholders involved in decision-making at the range of sub-basin scales, to understand they water data needs, potential/desired uses and capacities.
In March, the IWC team spent time with our Vietnamese partners, the Institute of Water Resource Planning (MAE) at their offices in Hanoi, progressing the detailed design of the research. The team initially sought to better understand the governance arrangements for sub-basin level agricultural water management, including differences in governance between surface and groundwater. There were lengthy discussions about who were the water use decision makers, spanning irrigation operators through to planners and managers in irrigation companies, commune, district, provincial and national levels. The paucity of information about the characteristics of these decision-makers reflected both the limited previous attention to engaging at the level of sub-basin managers, as well as the recent significant government reforms. The initial focus of the research with the stakeholders is to understand sub-basin water management in terms of roles and responsibilities, tasks, water issues and decisions being made, water data to inform decisions, data systems being used, potential capacity and barriers to using water accounting and similar datasets, and relationships between agencies.
The social research team developed methodologies that will be used to engage with these stakeholders over the life of the project, to inform the development of useful, accessible, and feasible sub-basin water accounting tools, drawing on remote sensing data as appropriate.
The technical team reviewed the different water accounting tools and it was decided that a tool based on a simplified Water Accounting plus framework would be the most suitable for the project as it was developed specifically for agricultural water management and for use with remote sensing data. The team focused on identifying a suitable case study area, that can use a simplified water balance to validate the tools and processes, with appropriate hydrogeology and identified subbasins of the Srepok River, ranging in size from large (10000 km2) to small (250 km2) as well as irrigation districts (Clusters). These tools are going to be used at range of scales, to test the applicability of the approach to meet the data needs of decision makers at the different scales. These areas will be the focus on both technical assessments and initial stakeholder engagement.
Through this case study the project will assess the usefulness of freely-available, or low-cost, timely remotely-sensed hydrological data, for use in water accounting tools, or results taken from tool, to assist decision makers in the better management of agricultural water supplies. The project will also assess the feasibility, opportunities and strategies to apply such remote sensing and associated water accounting products to sub-basin water management within, and beyond Vietnam, based on findings of this research.