Groundwater Level Declination in Bangladesh: System Dynamics Approach to Solve Irrigation Water Demand During Boro Season

Abstract

Groundwater has been declining in Bangladesh since introduction of deep tube wells (DTWs) and shallow tube wells (STWs) in late 1970s. Seasonal variation of groundwater has been shifted upto 4 meters during last 34 years. During Boro seasons groundwater table dropped drastically than other seasons. This study hypothesized that groundwater extraction is much higher than the natural recharge plus percolated irrigated water. Farmer´s perception is that if they dig deeper the supply would not be a problem, which led uncontrolled use of shallow tube wells (STWs) to extract water from lowered zones. This study selected an area that is 20 km away from Dhaka city having intensive Boro production. Analyzing the interview data (to know about the practices by farmers at present and before) and Bangladesh Water Development Board groundwater table data, we tried to simulate the problematic scenario with the help of simulation software called iThink. To address the problem 3 different policies have been investigated to achieve sustainable solution of the problem. The chosen policies were-(1) Harnessing only groundwater; (2) Alternative cropping; and (3) Depending more to surface water. The simulation results show that alternative cropping and going for surface water could solve the problem as well as able to restore the groundwater to its previous condition. But moving to surface water is a passive solution independent to farmers´ decision. Understanding the problem of groundwater declination by farmers was not so apparent. Farmers never thought of possibility of restoring groundwater table. The study suggested that alternative crop cultivation by replacing Boro rice would be the best sustainable solution not only to halt groundwater declination but also to restore the groundwater table. iii TABLE OF CONTENTS FOREWORD I ABSTRACT II TABLE OF CONTENTS III 1. INTRODUCTION 24 5.3.2 behavior testing 5.4 POLICY 3: Maximize surface water use 25 5.4.1 goal of this policy 5.4.2 background of the policy 5.4.1 Design of policy 3 5.4.2 Behavior testing 6. IMPLEMENTATION 6.1 Social feasibility 27 6.1.1 summary 6.2 Economic feasibility 28 6.2.1 summary 6.3 Technological feasibility 29 6.3.1 summary 6.4 Comparison of policies and challenges 30 6.5 Sustainability 31 7. CONCLUSION 7.1 Limitations of the study 32 7.2 Useful findings 32 7.3 Prospective future 33

An Integrated Method for Identifying Present Status and Risk of Drought in Bangladesh

“…Therefore, considering the finding of this study that "there is meteorological drought in NWB" and the finding from existing literature [12,56,59,60] that the "underground water table is declining in an unsustainable manner due to large abstraction for irrigation", it is highly likely that there will be an imbalance between the availability of underground water and requirement for irrigation. The probable scarcity of underground water in the future may transform the existing meteorological drought into severe agricultural drought, which is at present is observable in only a small part of the study area (NWB).…”

“…It is obvious that at present, the groundwater based-irrigation systems, in NWB and throughout Bangladesh, not only significantly reduced the severity of drought, especially in the pre-monsoon season, but also helped meet the increasing food demands of the rapidly growing population in Bangladesh [12,56,57]. However, there is a growing concern that the groundwater table in NWB as well as the other parts in Bangladesh is gradually declining in an unsustainable manner due to large abstraction by the irrigation projects [58][59][60]. Prior to the widespread abstraction of groundwater for irrigation, water tables in the mostly unconfined aquifers of Bangladesh were generally shallow with a weak seasonal fluctuating trend [56].…”