Groundwater in Bangladesh: Implications in a Climate-Changing World

 Edward McBean1, Andrew deJong, & Bahram Gharabaghi

1 Professor of Engineering and Canada Research Chair in Water Supply Security, A Dean of College of Physical and Engineering Science, University of Guelph; Guelph, Ontario, Canada; E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Abstract

The basis for, and magnitudes of, groundwater withdrawals in the developing world are described. A case study applied to Bangladesh, assessing trends projected in response to climate change, is used to project the challenges that will likely arise in terms of sustainability of the groundwater resources. The climate change predictions indicate that there will be a continuation of historical trends of increased temperatures, and concomitant increases in evapotranspiration. As well, although the climate change predictions indicate that there will be increased precipitation intensities, the increases will be during the wet months, with actually lesser intensities in the dry months. Hence, the implications of climate change are that the sustainability of the groundwater as resource to meet the irrigation needs, is projected to become increasingly difficult in the years ahead.

Keywords: Climate change, groundwater, sustainability, evapotranspiration, precipitation, temperature projection

 

 

Introduction

Globally, ground water use has undergone dramatic expansion over the past 50 years, with global abstraction rates increasing from an estimated 100-150 km3 in 1950 to 950-1000 km3 in the year 2000 (Shah et al., 2007). Much of this growth is the result for agricultural irrigation where, for example, in Bangladesh, the area irrigated by groundwater (as a fraction of total irrigated area) grew from 4% to 70% between 1972 and 1999 (Mainuddin 2002). This type of dramatic transformation where expansive areas are now being irrigated by groundwater has also been witnessed in other developing countries, including India at 53 percent, China at 16 percent, Pakistan at 31 percent, and Iran at 50 percent (FAO, 2005). The highest concentration of water use is in agriculture, as irrigation accounts for 70% of groundwater use worldwide (Brown et al., 1999, as reported in Kemper 2007).

In addition to dramatic growth in agricultural extraction rates, increased water demands are also occurring in response to rapid urban growth and to the population explosion where 55 to 60 percent of the population in India, and 60 to 65 percent in Pakistan, as examples, are dependent upon groundwater extractions (after Shah et al., 2003).

The importance of groundwater as a source of water supply is readily apparent, to meet in-country water needs.

Figure 1 (information extracted from FAO (2005)) depicts the area of agricultural lands and the share (%) under groundwater irrigation, for several countries. Of particular relevance are the very substantial magnitudes in these countries which rely upon groundwater for irrigation water.

Relevant also is that increasing water needs are causing greatly increased interest in water diversion to assist irrigation within a country. In-country diversion of water such as is occurring in India from the Ganges by the Farruka Barrage down to Calcutta, has ramifications to downstream countries in terms of opportunities lost due to lower river levels and will result in lower recharge to groundwater. The impacts are most dramatic during the dry seasons when the demand for water from rivers is the highest.

The results from these growths in water demand are so large in the developing world, in particular, that serious questions exist in terms of the sustainability of groundwater as a resource. When compounded by climate change and continued population growth, of concern is the degree to which increased groundwater withdrawals are sustainable to meet water supply needs.

This paper describes relevant dimensions of groundwater withdrawal characteristics, with a case study application to Bangladesh, to develop estimates of implications in terms of the sustainability of groundwater resources.