Management of Irrigation and Drainage Systems

Hector M. Malano, Paul van Hofwegen

• Publisher: CRC Press
• Year: 2018
• Topic: Technology & Engineering
• eBook ISBN:
  9781351434232
• Subtopic: Civil Engineering
• Index: Technology & Engineering

This monograph provides an overview of the principles required for a service orientation in the management of irrigation and drainage systems. The material covered is designed to emphasize an area largely neglected in the irrigation and drainage management literature. The dominating philosophy underlying this book is that irrigation and drainage systems must be managed as a service business responsive to the needs and changing requirements of its customers. It is postulated that this service approach to the management of irrigation and drainage systems consitutes a key element of the startegy that is needed to improve the current level of performance of many irrigation and drainage systems worldwide. Enhanced performance of irrigation is a prerequisite if we are to face the enormous challenge of producing greater quantities of food to meet the demand of a growing population. This is particularly the case in an environment with increasing competition for water from industry and urban water users, set against mounting concerns about environmental sustainability.

Chapter 1

The Context of Irrigated Agriculture

The management of an irrigation system has for its purpose the delivery of water to agricultural lands at such times and in such quantities as will enable the irrigator to produce the largest and best crops. The success of the manager is largely measured by the success of the farmer.

F. H. Newell, 1916

Irrigation and drainage play an important role in global food and fibre production. However, growing water scarcity, inappropriate management of water and irrigation and drainage infrastructure, and declining soil fertility in many regions of the world are beginning to constrain future increases in output. The future increase in food demand has to be satisfied by making better use of present irrigated area as the potential for expansion is limited by the availability of and the increased competition for good quality land and water. Improving irrigation and drainage system management is therefore a necessity to achieve the full potential of agriculture and increase productivity in a sustainable way. Moreover, management reform is imminent because of increasing competition for public funds.

1.1 THE IMPORTANCE OF IRRIGATION AND DRAINAGE

Over 275 million hectares of land are currently irrigated in the world. There has been a steady increase in newly irrigated land of the order of 4 million hectares or 1.5 percent per year over the last decades. In addition, some 150 million hectares is provided with a drainage system only. The new schemes were responsible for a remarkable increase in the production of rice, wheat and other crops. Figure 1.1 illustrates this trend in irrigated area. For many countries this development resulted (temporarily) in self-sufficiency in food crops and some countries even developed an export capacity. However, this achievement is threatened by a growing population, a larger per capita consumption, a degradation of the available land and water resources and a heavier competition for use of these resources.

Figure 1.1 Evolution of irrigated area 1950 – 2020 (source: Plusquellec 1988, Rosegrant e.a. 1997)

1.1.1 Population Growth

The world population is now almost 6 billion and is expected to increase at a rate of some 80 million a year during the next quarter century, increasing world population by 35 percent to 7.7 billion in 2020 (United Nations, 1996). The low population growth projections indicate a stabilisation of the world population at around 8 billion over the next 40 years. Medium and high projections expect the world population to grow to 10 and 12 billion people respectively by the year 2050. More than 95 percent of the population increase is expected to occur in developing countries, whose share of global population is projected to increase from 79 percent in 1995 to 84 percent in 2020. Over this period, the absolute population increase will be highest in Asia, but the relative increase will be greatest in Sub-Saharan Africa, where population is expected to almost double by 2020 (Pinstrup-Andersen et al, 1997).

1.1.2 Per Capita Annual Renewable Water Resources

Unless properly managed, fresh water resources may well emerge as the key constraint to global food production. The world annual per capita, internal renewable water supply is about 7,000 cubic meters at present. This per capita supply varies greatly between and within countries and seasons. In some countries like in the Middle East and North Africa, the annual per capita supply is often less than 1,000 cubic meters. With a continually growing population, per capita water availability is declining steadily. The UN’s 1994 medium population projection suggests that by the middle of the coming century, 4.4 billion of the nearly 10 billion people projected to inhabit the planet will live in 58 countries experiencing either water scarcity or water stress¹ (Population Action International, 1995).

The overall amount of water resources diverted for various uses is low. On this basis, it would appear that there are no major water resource constraints to further development of new irrigation areas. Global figures however tend to mask the marked regional differences in water resources availability. The reality is that there are many river basins in the world where water resources development has reached nearly full utilisation like the River Nile. Others such as the Mekong Basin in Vietnam, while being in an overall favourable water quantity situation, have limited capacity for agricultural expansion because of temporal variability of flows unless supply augmentation is pursued by additional regulation capacity.

1.1.3 Increasing Competition for Fresh Water

Water use by irrigated agriculture is very high compared with other uses. Worldwide, approximately 70 percent of water withdrawals are attributed to irrigation (FAO, 1996). Table 1.1 illustrates the water use by sector and by continent.

Table 1.1 Water consumption by sector and by continent (after FAO, 1996)

The demographic distribution of countries is rapidly changing with the urban areas growing faster - population growth plus urbanisation - than the agricultural population in all developing countries. Overall predictions for the year 2000 project that 50 percent of the global population will live in urban areas but rising to over 60 percent by 2025 (Serageldin, 1995). As a consequence, significant increases in demand for domestic and industrial water supplies can be expected.

This rapidly growing domestic and industrial demand for water will have to be met from reduced use in the agricultural sector. Projections of water demand of the International Food Policy Research Institute (IFPRI) indicate that global water withdrawals will increase by 35 percent between 1995 and 2020 with more than 80 percent of the increase being for industrial uses in developed countries (Pinstrup-Andersen et al, 1997). The share of domestic and industrial uses in developing countries is projected to double from 13 percent in 1995 to 27 percent in 2020. The more intensive use will also increase water quality degradation. Additional protective measures are required to safeguard the freshwater and soils from this increased urban pollution.

Competition among water uses already affects irrigated agriculture, especially in the water scarce regions in the semi-arid and arid zones. This pressure will become more severe and conflicts will increase as water supplies become more fully utilised. Solutions to these conflicts will require revisions of water law and systems of water property rights and water allocation. It is argued that in future, the price of water will be more closely related to its real economic value. This certainly will affect irrigated agriculture because the value of the marketable product per unit volume of water consumed is low. For example, only about 1 kg of maize grain can be produced in arid and semi-arid areas per cubic metre of water. For many semi-arid and arid areas, it will not be economical to import 1 ton of water for agriculture to produce 1 kg of grain even if renewable water was available. These areas will more likely be forced to use more local water for domestic purposes and import food² requiring increased expenditure in foreign currency.

1.1.4 Declining per Capita Arable Land

Soil is a basic, finite natural resource that is not renewable within a reasonable time frame. Only half the potentially arable land area of 3,200 million hectares is presently cultivated (Lal et al, 1988). Lal and Pierce (1991) indicate that the world per capita arable land area will progressively decline from 0.23 hectare by the year 2000 to 0.15 hectare by 2050, and to about 0.14 hectare by the time the world population stabilises in the year 2100. They also estimate that the minimum per capita arable land needed for an adequate diet is 0.5 ha under a modest level of inputs. The productivity of agriculture under rainfed, drained or irrigated conditions, must therefore increase to offset this decline in available area. Restoration of degraded lands is an ecological and socio-economic necessity to meet the basic necessities of the earth’s inhabitants, including its human and animal populations (Lal and Stewart, 1992).

In the longer term, there can be no doubt that dramatically more food will need to be produced to meet the demands of a projected 8 billion mouths to be fed by 2020. A recent study by the International Water Management Institute (IWMI) (Seckler et al, 1998) concluded that that perhaps 80 percent of increase in food supply will have to be met from irrigated lands, due to production limitations in dry land areas in the developing world. Others, such as the late Ian Carruthers (1993) have suggested, controversially, that the bulk of the world’s food supplies will eventually be grown in temperate Europe, North America and the Russian sub-continent.

1.2 DISAPPOINTING PERFORMANCE OF IRRIGATION AND DRAINAGE SYSTEMS

Despite the impressive gains in global food production during the last decades, policy and decision-makers in governments and in development institutions have raised criticism and concern on the performance and sustainability of irrigated agriculture.

The performance of many irrigation and drainage systems is significantly below their potential due to a number of shortcomings including:

♦ poor initial design as a result of inadequate operational specifications, or design assumptions which were not or could not be fulfilled following construction and commissioning of the works;

♦ distribution system layout did not adequately reflect existing land tenure or family/community associations in farm management;

♦ poor, improper or inadequate management environments;

♦ poor management systems within the managing organisations.

The most obvious manifestation of these shortcomings is unreliable main system water supply and poor maintenance practices. Improvements in on-farm water management are often hampered by the unreliability of water supply. Users are not motivated to organise themselves and participate in the operation and management of the water delivery system, and neither willing to pay water charges if the service is poor and unreliable. Furthermore, insufficient funding for maintenance and ineffective use of these funds results in problems of rapid deterioration of the irrigation and drainage infrastructure leading to further problems such as inequities in water distribution and reduced productivity. Combined with a lack of adequate drainage infrastructure, poor irrigation water management has been accompanied by soil degradation arising from waterlogging and salinisation of the irrigated cropland. To date, some 25 million hectares have become virtually unproductive as they are severely affected by these problems.

The earth summit in Rio de Janeiro (United Nation Conference on Environment and Development/UNCED, 1992) scrutinised the irrigation sector and its environmental impact and sustainability in that:

♦ Irrigation uses too much water: about 70 percent of global fresh water use;

♦ Irrigation leads to waterlogging and salinity: some estimates indicate that over 50 percent of the world’s irrigated land has developed drainage problems, and some 24 percent is affected by yield reduction from salinisation;

♦ Irrigation pollutes freshwater resources: through release of insecticides, pesticides and other agro-chemicals, and saline drainage effluents;

♦ Irrigation affects human health: by creating habitats for vectors of water related diseases.

In addition to these issues, there is a widespread concern about the financial sustainability of irrigation. Investment costs for developing public irrigation schemes are almost always partly or fully subsidised and the recurrent cost of operation and maintenance is hardly ever fully recovered from the users. This means that irrigation often represents a permanent drain on government treasuries.

The rapid deterioration of the irrigation infrastructure worldwide is very severe. Most of the investment in irrigation development during the 1950s and 1960s was for development of new irrigated lands. Poor operation and maintenance practices have often resulted in a significant reduction in the economic life of the infrastructure and the concurrent loss of capacity to provide an effective water supply to farmers. Beginning in the 1970s until the present the emphasis of investment strategies progressively shifted towards rehabilitation and modernisation. Many irrigation schemes developed over the last decades have undergone periodic rehabilitation work as a result of premature decay of the infrastructure leading to the typical cycle of construction-deterioration-rehabilitation (construction). This recurrent need for rehabilitation of existing infrastructure confirms the lack of sustainability and other problems indicated above.

This cyclic infrastructure problem has been ascribed primarily to a lack of adequate funding for conducting appropriate maintenance. While this is the immediate cause of the problem, in fact it is the result of a lack of an appropriate and sustainable management framework. Such framework is needed to enable:

♦ The identification of the true cost of operating and maintaining an irrigation scheme;

♦ The implementation of appropriate policies to ensure that the level of revenues is sufficient to cover these costs.

The lack of sustainability has been one of the major factors in reducing the level of investment in new irrigation development. Moreover, future investments and development in irrigation are likely to be more difficult because of increased competition with other water uses and higher development costs for new projects as most low cost projects have already been developed. Worldwide, the irrigated area is projected to grow at an average annual rate of 0.6 percent per year during 1995 - 2020, less than half the annual growth rate of 1.5 percent during 1982 - 1993 (Pinstrup-Andersen et al, 1997).

The future challenges for the irrigation and drainage sector will be to develop and maintain a financially and environmentally sustainable operation that will enable it to meet:

♦ future food demand to keep pace with world population growth,

♦ increased competition for water between agricultural and non-agricultural users; and,

♦ a reduction in available agricultural land.

To meet these challenges, irrigation and drainage requires an integrated management of land and water resources that combine management of

♦ the water balance;

♦ the nutrient and salt balance;

♦ the financial balance.

1.3 GOVERNMENT POLICY AND PLANNING ENVIRONMENT

Until recently, substantial capital subsidies were justified in the name of food self-sufficiency and equitable distribution of benefits to subsistence farmers. It was often the intention of development agencies and national governments to obtain full payment of operational costs from the users. However, fee levels have consistently lagged behind the real costs of service and maintenance, and collections rates have varied from dismal (less than 10%) to poor (around 50%) in most countries. Faced with declining te...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• PREFACE
• ACKNOWLEDGEMENTS
• ABBREVIATIONS AND ACRONYMS
• 1 THE CONTEXT OF IRRIGATED AGRICULTURE
• 2 THE MANAGEMENT ENVIRONMENT OF IRRIGATION AND DRAINAGE
• 3 MANAGEMENT PROCESSES OF THE ORGANISATION
• 4 THE IRRIGATION AND DRAINAGE SERVICE CONCEPT
• 5 RELATION BETWEEN LEVEL OF SERVICE, FLOW CONTROL AND MANAGEMENT
• 6 MANAGEMENT OF IRRIGATION AND DRAINAGE INFRASTRUCTURE
• 7 PERFORMANCE OF IRRIGATION AND DRAINAGE SERVICE
• 8 THE WAY FORWARD
• REFERENCES