Water Harvesting for Groundwater Management

Issues, Perspectives, Scope, and Challenges

Partha Sarathi Datta

• Publisher: Wiley-Blackwell
• Year: 2018
• Print ISBN: 9781119471905
• eBook ISBN: 9781119472025
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Hydrology

Outlines the concept and principles of water harvesting for groundwater management for an international audience, and looks at the positives and negatives surrounding water harvesting technologies

This book is the first to fully outline the concept and principles of water harvesting for groundwater management for a global audience. It offers guidance to academics, students and researchers on effective water harvesting approaches for groundwater recharge, and educates them on the risks associated with managed aquifer recharge, as well as the causes of success or failure of particular management strategies, and demand management strategies and tools. The book is helpful to water managers, administrators, and professionals, to make decisions to allocate resources; developing innovative cost-effective measures and approaches to achieve demand-supply balance. The book provides readers with an overview of the historical evolution of water harvesting for groundwater recharge. It looks at the benefits and gaps in knowledge, their implementation and funding strategies, and public participation. It also assesses the strengths, weaknesses, opportunities, and threats (SWOT) of water harvesting technologies.

Water Harvesting for Groundwater Management: Issues, Perspectives, Scope and Challenges offers chapters covering: issues on water harvesting and water security; mega-trends that impact water security; groundwater occurrence, availability, and recharge-ability; phases of water harvesting systems; SWOT analysis of water harvesting systems; case studies and short examples of implementing water harvesting; scope of water harvesting for GWM strategies; guidelines to make water harvesting helpful and meaningful for GWM; and more.

• Summarizes the theories and applications of water harvesting for groundwater management for a world audience
• Offers guidance on effective water harvesting approaches for groundwater recharge, managed aquifer recharge, and successful water management strategies
• Evaluates the strengths, weaknesses, opportunities and threats (SWOT) of water harvesting technologies
• Part of the Challenges in Water Management series

Water Harvesting for Groundwater Management: Issues, Perspectives, Scope and Challenges is an excellent resource for water management professionals working with water harvesting technologies, and will be of great interest to water managers, administrators, professionals, academics and researchers working in water management.

1
Introduction: Issues in Water Harvesting and Water Security

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CHAPTER MENU

• 1.1 Concept/Principles of Water Harvesting and Water Security
• 1.2 Food‐Water‐Energy Nexus
• 1.3 Climate Forcing Environmental Impacts (Floods and Droughts)
• 1.4 Water Security

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1.1 Concept/Principles of Water Harvesting and Water Security

Rainwater harvesting (RWH) is not a new concept. The basic principle of water harvesting (WH) is to capture rainfall and high‐intensity rainfall‐induced surface runoff in one area and transfer it to another water‐scarce area, thereby increasing the amount of water available in the latter. The concept of water security has its genesis in the need to shift focus to demand‐side water management from supply‐side, so that water is available in adequate quantity, during both normal and typical conditions. It became clear long ago that water systems should be considered as a whole, since water quantity and water quality issues on rainwater, surface water, and groundwater resources are linked. However, the term “water security” has taken a central position recently associated with other popular terms such as “food‐water‐energy nexus,” “water hazard,” “water risk,” “water vulnerability,” “water resilience,” “sustainable water resources management,” “integrated water resources management,” and “adaptive water management.”

The term “water security” is generally associated with other terms such as “integrated,” “sustainable,” and “adaptive.” However, achieving water security, in practice, requires interinstitutional and interdisciplinary integration across the boundaries of many sectors, such as political, administrative, governance, biophysical, social, infrastructural, economic, and financial, most of which lie outside the direct realm of water, to reduce competition or even conflict over water resources. Development studies often consider the national scale, hydrological studies generally employ a catchment scale, and social scientific studies usually focus on the community scale. Therefore, water security at household, local, urban, rural, state, regional, country, or global level is likely to have very different meanings. WH and water security have been therefore defined in a number of ways, and can be grouped as in situ and ex situ types, and it is necessary to clearly assess the potential of RWH in reality, depending on the source, availability, and volume of water.

1.1.1 Source of Water and Its Availability

The primary source of water is rainfall. Globally, the exposed land surfaces receive approximately 113 000 km³ of rainfall each year. Of this, approximately 41 000 km³ (or 36%) is surface runoff, which replenishes rivers, streams, and lakes. The balance (64%) is evaporated via vegetation, soil, and water surfaces.

Easy access to water and its adequate availability is essential for living beings, domestic, agricultural, industrial, and economic development purposes. Although, globally, enough water exists, its supply has reduced due to growing population demand for water for domestic, agriculture, energy production, manufacturing, and healthcare purposes, and via pollution. In many countries, where water supply comes mostly from surface water bodies, pollution of rivers and lakes and the non‐availability of adequate quantities of good‐quality water supply has lead to increased dependence on groundwater. This has resulted in indiscriminate extraction of groundwater in excess of the natural recharge in many areas, causing substantial decline in groundwater levels and yields of many dug wells and tube wells.

The increase in groundwater abstraction, associated with population growth and increasing demands for water, food, and income, began during the first half of the twentieth century in a limited number of countries such as Italy, Mexico, Spain, and the USA. However, the periods of maximum growth were not simultaneous, and varied from country to country: 1950–1970 in the United States, 1960–1990 in India, and 1975–2000 in China. The most pronounced increase in extraction has been in those countries where current groundwater withdrawals are the highest. In the 1960s, a second phase started in parts of South and East Asia, the Middle East, and northern Africa. In the 1990s, a third phase started, including some South and South‐East Asian countries such as Sri Lanka and Vietnam, and also sub‐Saharan Africa. In the developed countries, stabilizing/declining trends followed a strong but variable increase in abstraction of groundwater in the earlier stages.

For example, in the USA, in 30 years (1950–1980), abstraction increased by 144%, followed by a temporary decline but a stable average during 1980–2005. In Japan, in 30 years (1965–1995), abstraction increased by 60%, before declining by 13% during 1995–1999. In several European countries also, although extraction was generally at lower levels, periods of marked growth have been observed; for example, in the UK, more than 54% of growth occurred in 25 years (1950–1975); in Denmark, more than 70% in seven years (1970–1977); in Spain, more than 15% in 10 years; and in The Netherlands, more than 12% in five years (1971–1976). In Australia, groundwater abstraction almost tripled in 30 years (1970–2000). In Germany, Belgium, France, Sweden and Canada, groundwater abstraction remained relatively stable over time. Since the beginning of the twenty‐first century, almost all European countries have demonstrated stabilization or slightly declining groundwater abstraction trends.

In developing countries, such as India and China, with increasing demographic and economic growth, increases in groundwater abstraction have generally been observed from the period 1970–1980 onwards, especially where irrigation has expanded significantly. Large increases have occurred in countries of the arid and semi‐arid zone where oil revenues facilitated deep groundwater (including non‐renewable resources) to be withdrawn for irrigation. Total groundwater withdrawal increased by a factor of 11 in Libya during 1970–2000; by 10 in Saudi Arabia during 1975–2000; by 6 in Egypt during 1972–2000; by 3.3 in Iran during 1965–1995; and by 3.2 in Tunisia during 1977–2000. During the last 50 years, easy accessibility of groundwater and its local availability have increased the number of shallow wells. On the other hand, public affordability for sinking tube wells has increased due to technological developments in construction of deep tube wells, water abstraction devices and pumping methods, provision of free or subsidized electricity for pumping in many parts, and easy credit availability from financial institutions.

Globally, this has resulted in indiscriminate extraction of groundwater in excess of the natural recharge in many areas, causing substantial decline in groundwater levels and yields of many dug wells and tube wells, particularly during the summer. It has become difficult for resource managers to co‐ordinate users of the same aquifers across wide geographic spaces. Over the last few decades, increasing groundwater depletion and degradation in India and other parts of the world, and ecologically damaging, socially intrusive, capital‐intensive, and unsustainable water resource development projects implemented so far have forced people to find alternative sources of water supply. These problems have forced people to consider local RWH, conservation, and reuse for agriculture, irrigation, and other purposes. Globally, from time immemorial, people were aware that groundwater augmentation by artificial recharge and WH by collecting, storing, and conserving of local rainwater surface runoff on natural catchment areas on rocky surfaces, hill slopes, rooftops, and artificially prepared impervious/semi‐pervious surfaces may provide augmentation of water supply.

1.1.2 Concept and Definition of Water Harvesting

The RWH concept employs a wide range of approaches and technologies to collect and store rainwater. WH has been defined and classified in a number of ways, and can be grouped as in situ and ex situ types, depending on the source of the collected water.

1. In situ RWH technologies are soil management strategies that enhance rainfall infiltration and reduce surface runoff.
2. Ex situ RWH collects surface runoff water from areas such as rooftops, land surfaces, steep slopes, road surfaces or rock catchments for storage in tanks. Depending on the size of the storage, ex situ RWH systems can be further divided into passive and active systems.
   • Passive systems (e.g. rain barrels) are small‐volume (50–100 gal) systems that capture rooftop runoff without treatment. The captured water is generally not used for drinking purposes. Due to their size, passive harvesting systems are commonly used in residential applications.
   • Active systems (e.g. cisterns) are of relatively larger volume (1000–100 000 gal) and capture runoff from roofs or other suitable surfaces such as terraces and road surfaces. Active harvesting systems provide water quality treatment and can be used on a community level.

Commonly, the terms WH and RWH are synonymous and used interchangeably. The main difference is with respect to breadth and scope. Most of the definitions are similar and closely related, and WH is generally defined as: “The collection and management of high intensity rainfall induced water runoff and/or floodwater to increase water availability for domestic and agricultural use as well as ecosystem sustenance.”

1.1.2.1 Why Harvest Rainwater?

Important reasons for harvesting rainwater include the following:

• For centuries, it has been the simplest indigenous technology, being practiced in India and many other parts of the world.
• To conserve surface water runoff during the monsoon.
• To reduce soil erosion.
• To arrest groundwater decline and augment the groundwater table.
• To improve water quality in aquifers.
• To inculcate a culture of water conservation.
• Self‐sufficiency, less expensive, and ease of maintenance.

1.1.2.2 Aims of Water Harvesting

The aims of WH are essentially to collect surface runoff from areas of surplus and to store it in over‐ or underground storage, to recharge groundwater levels, deliberately reallocate water resources over time within a landscape and make it available to places where there is water shortage. This increases the availability of water by (i) impeding and trapping surface runoff, (ii) maximizing water runoff storage, and (iii) harvesting subsurface groundwater. Water harvesting makes more water available for domestic, livestock, and agricultural use by buffering and bridging drought spells and dry seasons through storage. Water harvesting captures water for domestic use, replenishes green water supplies, or increases blue water availability locally. New methods and mechanisms are being developed all over the world to conserve water as far as possible in all sectors. Our predecessors also adopted concepts of water recharge, which are still practiced today. However, with time, improvements in technology have introduced new recharge techniques to achieve better results.

1.1.2.3 Principles, Concept and Components

The basic principle of WH is to capture rainfall in one area and transfer it to another water‐scarce area, thereby increasing the amount of water available in the latter. Water harvesting is seen as an integral part of sustainable land and water management. Water harvesting and runoff recycling has six basic components: a catchment or collection area, collection (harvesting) of excess rainfall, runoff conveyance system (including lifting and conveyance), water application area, efficient storage of harvested water, and optimal utilization of applied water for maximum benefits. In some cases, the components are adjacent to each other, in other cases they are connected by a conveyance system. The storage and application areas may also be the same, typically where water is concentrated in the soil for direct use by plants.

1.1.2.3.1 Catchment or Collection Area

The area where high‐intensity rainfall‐induced runoff is harvested. The catchment area may be a few square meters to severa...

Table of contents

• Cover
• Table of Contents
• Series Editor Foreword – Challenges in Water Management
• Foreword
• Preface
• 1 Introduction
• 2 Mega‐Trends that Impact Water Security
• 3 Groundwater Occurrence, Availability, and Rechargeability
• 4 Phases of Water Harvesting Systems
• 5 Case Studies of Implementing Water Harvesting
• 6 SWOT Analysis of Water Harvesting Systems
• 7 Challenges Associated with Water Harvesting
• 8 Scope of Water Harvesting for Groundwater Management Strategies
• 9 Guidelines to Make Water Harvesting Helpful and Meaningful for Groundwater Management
• 10 Concluding Remarks
• Glossary of Terms
• Index
• End User License Agreement