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Modeling artificial groundwater recharge and low-head hydroelectric production: a case study of southern Pakistan

Date

2016

Authors

Siddiqui, Rafey Ahmed, author
Bailey, Ryan T., advisor
Grigg, Neil S., committee member
Sale, Thomas, committee member
Sanford, William, committee member

Journal Title

Journal ISSN

Volume Title

Abstract

DHA City Karachi (DCK), a city designed for approximately one million people, is envisaged to become a satellite city to the second largest city in the world, Karachi, which has a population of 25 million. The upcoming city is located 21 miles north of main metropolitan Karachi in the arid southern part of Pakistan. The region receives little rainfall with an annual average of 217 mm and temperatures ranging from an average of 88°F in the summers to 68°F in the winters. The town has a projected water demand in the fully developed stage of 45 Million Gallons per Day (MGD) and 500 Mega Watts (MW) of electricity. Since water and electricity are prized and expensive commodities in the region, alternate and renewable sources of both need to be explored for DCK to meet its goal of sustainability and conservation. Two options for these sources, artificial recharge and hydroelectric product, are explored in this study. Artificial recharge to replenish groundwater resources is becoming more common in arid areas. In this thesis, the capacity of small lakes to produce significant seepage and recharge to the underlying aquifer within city limits is explored for DCK. The lakes are fed by treated effluent from Sewage Treatment Plants (STP), which then ponds and creates downward seepage to the water table. Artificial recharge and resulting groundwater flow within the aquifer is simulated using a three-dimensional groundwater flow model (MODFLOW). A variety of pumping scenarios are explored to determine the quantity of groundwater that can be pumped for water supply. An optimal placement of 50 pumps throughout the city also is determined, with drawdown used as the variable to be minimized so as to minimize pumping costs. In the fully developed stage of artificial recharge, the lakes feed almost 7.9 MGD of water to the aquifer, out of which 6.6 MGD can be pumped out and consumed sustainably on a daily basis through the 50 planned wells. Since DCK is to be developed and inhabited in 3 phases, analysis revealed that quantities of 1.4 and 3.5 MGD can be pumped out sustainably for the short and mid-term developmental plans. A sustainable hydroelectric system was also designed for using the hydraulic structures of the small lakes. System control was introduced by application of Artificial Neural Networks (ANN) and Model Predictive Control (MPC) to maintain the hydroelectric potential and constant head against variation in flow as delivered from the STPs. The results show an output of 13.92 MW of green and sustainable hydroelectricity which can be produced at a very low cost. A cost-benefit analysis projects a savings of $11,550 and $60,000 per day due to the artificial groundwater recharge and hydroelectric production respectively, with the cost of construction of these projects being paid off within 5 and 2 years at this rate, including the cost of operation and maintenance. Results, however, should be used with caution due to the preliminary nature of the models and calculations.

Description

2016 Spring.
Includes bibliographical references.

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Subject

groundwater
hydrology
small dams
hydroelectricity
artificial recharge
renewable energy

Citation

Associated Publications