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Rainwater Harvesting in Cholistan Desert: A Case Study of Pakistan

Muhammad Akram Kahlown9

Abstract

About 70 million hectares of Pakistan fall under arid and semi-arid climate including desert land. Cholistan is one of the main deserts covering an area of 2.6 million hectares where water scarcity is the fundamental problem for human and livestock population as most of the groundwater is highly saline. Rainfall is the only source of freshwater source, which occurs mostly during monsoon (July to September). Therefore, rainwater harvesting in the desert has crucial importance. The Pakistan Council of Research in Water Resources (PCRWR) has been conducting research studies on rainwater harvesting since 1989 in the Cholistan desert by developing catchments through various techniques and constructing ponds with different storage capacities ranging between 3000 and 15000 m3. These ponds have been designed to collect maximum rainwater within the shortest possible time and to minimize seepage and evaporation losses. As a result of successful field research on rainwater harvesting system, PCRWR has developed 92 rainwater harvesting systems on pilot scale in Cholistan desert. Each system consists of storage reservoir, energy dissipater, silting basin, lined channel, and network of ditches in the watershed. The storage pond is designed to collect about 15000 m3 of water with a depth of 6 m. Polyethylene sheet (0.127 mm) on bed and plastering of mortar (3.81 cm) on sides of the pond was provided to minimize seepage losses. All these pilot activities to harvest rain have brought revolution in the socio-economic uplift of the community. These activities have also saved million of rupees during the recent drought. Large scales adoption of all these interventions would ultimately help improve the socio-economic conditions of the residents of hyper arid area of the country.

1. INTRODUCTION

Pakistan has 70 Mha arid and semi-arid lands that is about 80% of its total geographical area (PADMU, 1983). Out of 41 Mha arid area, 11 Mha falls under main deserts where climate is hyper arid (Kahlown and Majeed, 2004). These deserts are: Cholistan (2.6 Mha), Thal (2.3 Mha), Thar (4.3 Mha) and Chagi-Kharan (1.8 Mha) (Figure 1). The Cholistan is a big desert in the Punjab province which consists of sand dune, sandy soil, loamy soil, and saline-sodic clayey soil. Human population in the desert is about 0.11 million and livestock population is nearly 2.0 million. The population is scattered at different places on the availability of drinking water. Low and sporadic rainfall (166 mm average annual), high temperatures (up to 550 C in summer), low humidity, high rate of evaporation and strong summer winds are the main characteristics of the climate. The groundwater is mostly saline and unfit for human and livestock drinking (PCRWR, 2004a). Because of these limiting factors, the local population is nomadic and remains in search of water and fodder for their animals.

9 Chairman, Pakistan Council of Research in Water Resources (PCRWR), Khayaban-e-Johar, Islamabad - Pakistan, Ph: 0092-51-9258959, Fax: 0092-51-9258963, Email: kahlown@hotmail.com, pcrwr@isb.comsats.net.pk

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CHINA

I N D

I A

I R A N

A F G H A N I S

T A N

QUETTALoralai

Bannu

PESHAWAR

Rawal pindiISLAMABAD

Gilgit

Skardu

D.I.khan

Sargodha

Faisalabad LAHORE

Multan

Bahawalpur

Hyderabad

KARACHI

Khuzdar

Panjgur

Gowdar

Sukkur

A R A B I A N S E A

Indus R

iver

Indu

s R

iver

Indu

s Ri

ver

Indu

s R

iver

Sutlej River

RaviRive

rChenab R

iver

Jhel

um

River

CHOLISTAN

DESERT

THALDESERT

THAR DESERT

Kabul River

Chitr

al R

iver

Swat

Riv

er

N

KHARANDESERT

LarkanaR B O

D

L B O D

Shikarpur

Figure 1: Main Deserts of Pakistan

The primary source of freshwater in the Cholistan desert is rainwater, which is collected in natural depressions or man-made ponds locally called tobas. There are more than 1500 tobas in the desert out of which only 500 are in operation (PCRWR, 2004b). These tobas are mostly not in appropriate places because the sites have not been identified based on scientific information. Most of the rainwater collected in the tobas is lost through seepage and evaporation due to high infiltration rates in sandy soil and temperature with strong winds during summer season. Siltation in tobas is another serious concern, which reduces their storage capacities rapidly, especially during monsoon season. In order to improve the situation, PCRWR has been actively engaged in various research and development (R&D) activities to uplift the socio-economic conditions of the dwellers.

Rainfall is single source of freshwater in the desert. It has been investigated that there is about 350 million cubic meter (Mm3) runoff potential available for storage in the desert (Table 1). Results of the research studies conducted at Dingarh Station showed that drinking water requirements of the dwellers could successfully be met through collecting rainwater on scientific grounds.

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Table 1: Potential Runoff in the Cholistan Desert

Year Rainfall (mm) Potential Runoff (mm) Runoff for Storage in Cholistan (Mm3)

1989 84.2 38 168

1990 144.1 42 187

1991 173.0 87 385

1992 231.0 115 506

1993 155.9 89 392

1994 299.2 152 672

1995 213.0 131 582

1996 152.0 81 359

1997 201.0 74 327

1998 172.1 65 287

1999 20.8 3 14

2000 126.4 62 273

2001 148.6 50 222

2002 2.0 - -

2003 240.0 106 467

Average 160.5 79 350

2. DEVELOPMENT OF WATER HARVESTING SYSTEM

As a result of field research on rainwater harvesting techniques, PCRWR has initiated a 4-year Research and Development (R&D) Programme in 2001 to make water available in the desert for drinking. The activities were undertaken including reconnaissance survey to identify the suitable catchments, demographic survey to assess water demands, hydrological studies to assess the runoff potential of the catchment, topographic survey to determine the slope for runoff; development of catchments to establish a network of ditches, soil profile investigations to determine physical and chemical properties of the catchment/pond, design analysis of rainwater harvesting system to estimate the quantity of civil works.

3. COLLECTION OF RAINWATER

Alive to the problems faced by the population in the desert, 92 rainwater-harvesting systems have been developed on pilot scale. Each system contains the components like storage reservoir, energy dissipater (stair), boundary wall, silting basin, lined channel, and ditches network in the catchment. The storage pond is designed to collect about 15000 m3 (4.0 US million gallon) of water. The depth of the pond is 6 m. Polyethylene sheet (0.127 mm) on bed and plastering of slag mortar (3.81 cm) mixture of clay, quick lime, wheat straw and cement on sides of the pond have been provided to minimize seepage losses. The quantity of the mortar for one pond includes 6 m3 clay, 100 kg lime, 970 kg wheat straw, and 0.06 m3 cement. The energy dissipater having dimensions of 1 m wide and 23 cm each length and height along one side of the pond protects the sides and the bed of the pond from severe erosion expected from gushy water. Boundary wall does not only restrict the wild animals and livestock but also provides barrier against movement of sand by strong summer winds. A small silting basin controls the entrance of heavy sediments and debris in the pond. Each pond has been connected with the catchment through a lined channel, which has a network of ditches. It has been

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observed that all the constructed ponds got fill up to their full design capacity during the rainy seasons (winter or monsoon). Water quality analysis of the selected ponds illustrated that the water quality was within the permissible limits excluding turbidity level. In general practice, the livestock drink water from the pond directly. However, the dwellers keep this water in mud pot for few hours by adding alum treatment before drinking.

4. IMPACTS OF THE RAINWATER HARVESTING PROJECT

All these pilot activities have brought about revolution by creating awareness among the desert people and the concerned development agencies working in the area. This project has harvested about 368 million gallons of freshwater annually to meet drinking water requirements of human and livestock population. Moreover, this project has saved 6000 million rupees per drought in the form of livestock production due to reduction in livestock migration, mortality, diseases and damage of crops. Increase in production of livestock has also been observed in the form of meat, milk and other utilities besides reduction of migration of human and livestock from desert towards irrigated area.

5. CONCLUSIONS AND RECOMMENDATIONS

Following are conclusions and recommendations:

(i) Out of 350 Mm3 of runoff potential, 1.35 Mm3 has been harnessed successfully through scientifically designed 92 pilot rainwater harvesting systems. The remaining potential can easily be exploited through adopting rainwater harvesting strategy developed and tested by PCRWR;

(ii) About 368 million gallons of freshwater is economically made available through out the year against. However, maintenance of the system by local people is recommended to make it sustainable;

(iii) There is still need to carry out research endeavors to evolve the cheapest method for reducing evaporation and seepage losses from the ponds.

REFERENCES

Kahlown, M.A. and A. Majeed, 2004, Pakistan water resources development and management. Pakistan Council of Research in Water Resources.

PADMU, 1983, Country report Pakistan - Desertification problems, extent and remedial measures. Pakistan Desertification Monitoring Unit (PADMU), Islamabad.

PCRWR, 2004a, Research study on evaluation of impact of research and development projects implementation on desertification in Cholistan. Final Report. Pakistan Council of Research in Water Resources (PCRWR). Publication No. 129.

PCRWR, 2004b, Pre-project socio-economic analysis of 25 selected settlements in Cholistan desert. Pakistan Council of Research in Water Resources (PCRWR). Publication No. 130.