Water Provision Methods in Arid and Semi-Arid Areas in Iran - Case Study Example

WATER PROVISION METHODS IN ARID AND SEMI-ARID AREAS IN IRAN 1. Introduction In many parts of the arid Middle East, water shortages have become increasingly severe. Local subsurface and surface water resources are no longer adequate to meet the burgeoning needs throughout these regions. Although many governments and other investors in the Middle East have abandoned most of the traditional methods of water provision in arid and semi-arid regions for more modern but less sustainable methods, there is evidence of the existence of some of the traditional water harvesting and management methods in many parts of Iran. This report presents and analyses two of such methods: Qanat and Bandsar. It should be noted though that although these methods are ancient, they have been modified over time to conform to the present needs. The report will compare the two methods in terms of their nature, cost of construction, environmental impact and public acceptance. 2. Background Arid and semi-arid areas occupy over 80 percent of Iran’s land (Taghvaee abrishmi 2007, p. 429). Innovative approaches that have a very high potential for use in arid and semi-arid regions such as Iran have been established over the centuries. Water harvesting and management refers to a method of collecting and storing rainwater that can be used to meet domestic, agricultural and other needs. Surface runoff management techniques are frequently employed to raise the level of water infiltration and supply in addition to productivity in arid areas (Ghanbarpour, Ahmadi & Gholami n.d. p. 133). The water management systems presented in this report typically have four components: an area for management of rainwater, a system of channelling water for storage, storage tanks or reservoirs, and distributions systems to deliver water to the point of use (Ghanbarpour, Ahmadi & Gholami n.d. p. 134). 3. Presentation of the methods 3.1 Qanat A Qanat is a gently sloping subterranean tunnel dug deep enough into alluvium or a water-bearing sedimentary rock to perforate the underground water table and penetrate the aquifer below it (English, n.d. p. 188). Water from the aquifer infiltrates into the upper reaches of these channels, runs down along the gentle slope, and then emerges as a surface stream of water at a nearby settlement (English n.d. p. 188). Qanats are typically constructed on the slopes of features such as intermontane basins, piedmont alluvial fans, and along alluvial valleys. In such areas, collection of groundwater has brought water to the surface and this aids in settlement of people in regions where no other traditional methods of providing water would work (English n.d. p. 188). The first step for the construction of a Qanat is to sink a trial shaft to determine the presence of the water table as well as depth. When the shaft is sunk to reach the impermeable stratum, it can be used as a mother well. A tunnel is then dug towards the mother well to channel the water (Ghanbarpour, Ahmadi & Gholami n.d. p. 134). See fig. 1 for an illustration. Fig. 1: Vertical cross section along a Qanat as constructed in Iran Source: Ghanbarpour, Ahmadi & Gholami (n.d., p. 137) 3.2 Bandsar A Bandsar is a water harvesting and management system practiced where valley plains and mountainous catchments occur in close proximity. The runoff from the catchment accumulates in the lower valley floor enclosed by a small earthen dam (Ghanbarpour, Ahmadi & Gholami n.d., p. 135). A Bandsar has a very simple construction. It comprises a shallow water drainage which can be a seasonal stream, an embankment made of earth material from the stream sediment, and a water channel to remove overflow water. The runoff that is generated from an upland area is stored in the basin and slowly infiltrates. Sediment trapped from the Bandsar is also used for improving sandy soil for agriculture (Ghanbarpour, Ahmadi & Gholami n.d., p. 135). See fig. 2. Fig. 2: A plan for a Bandsar constructed in Khorasan province, Iran Source: Ghanbarpour, Ahmadi & Gholami (n.d., p. 136) The area of a Bandsar varies between about 20 m2 to some hectares. Where there are homogenous low steep slopes, the basins are designed to be larger; but where the slopes are steeper, the basin is designed to be smaller (Sabzevar & Hasheminejhad 2007, p. 447). 4. Requirements 4.1 Cost The cost of providing water refers to the monetary value expended in establishing a given water supply. It is important to determine the cost because not all areas have equal resources, and the resources available will determine the feasibility of the water provision project. 4.2 Environmental impact This refers to the possible positive or negative implications that a project may cause to the environment. It is important to because it helps to determine the ramifications of a project in advance. Environmental impact should be considered to determine if the positive impacts of a project outweigh the negative ones, and if so, what can be done to mitigate the negative consequences. 4.2 Public acceptance This refers to the extent to which the public agrees to a have a given project. It should be considered because for a project to be successful, it must be liked by the people for whom it is meant. Public acceptance is important because only when the affected people accept a project will they be willing to participate in its implementation and use. 5. Comparison 5.1 Cost The cost of constructing Qanats and Bandsars varies depending on a number of factors. For the construction of a Qanat, the factors that affect cost include the capital available, the stability of the ownership, conditions of the soil and underground water, the length of the Qanat, the volume of water required, the skills of those doing the work, and many social, environmental and economic factors. For instance, the cost constructing of a 55 metre deep Qanat was $11000 per square kilometre in the late 1960s (English n.d., p. 194). The cost of putting up a Qanat of length 40 km to the basin city of Kirman in Iran with a mother well of 90 m in depth was about $213,000 and was completed in 1950. Given the changes in economic factors such as inflation, the cost of building a Qanat today would probably be prohibitive (English n.d., p. 194). Although there are no precise figures on the construction of a Bandsar, this method should be slightly cheaper than establishing a Qanat because of the relatively fewer items and labour required in putting up a Bandsar. Unlike a Qanat which requires digging of a deep well, a Bandar entails very simple construction as mentioned above in this report. 5.2 Environmental impact Save for the digging and slight construction activities involved in establishing Qanats and Bandsars, the two schemes of water harvesting and provision are environmentally friendly. Rainwater harvesting is environmentally friendly because the process assists in recharging ground water, enhancing wetlands, forest conservation, ecological farming, and reduces the need to construct new dams for supplying water – thus facilitating ecological flow (Taghvaee abrishmi 2007, p. 432; Pathak & Heijnen n.d, p. 1). Qanats act as renewable resources because the rate of flow of water in a Qanat is regulated by the level of the underground water table (English, n.d., p. 195). Hence, a Qanat cannot drain an aquifer, since its flow varies proportionally with the subsurface water supply. Thus when properly maintained, a Qanat is a sustainable system that provides water to neighbouring settlements for an indefinite period. Qanats exploit underground water as a renewable resource and are therefore environmentally friendly. But again, because deep wells incorporated in the Qanat draw water from permanent aquifers on demand without consideration to the rates of recharge, this can be disadvantageous as it enables people to exploit water from the source in an unsustainable manner (English, n.d., p. 195). Bandsars are sustainable as well because the whole process leads to an increase in soil moisture, soil fertility and hence enhanced agricultural productivity (Taghvaee abrishmi 2007, p. 440). Bandsars also help to control flash floods (Taghvaee abrishmi 2007, p. 440). Notably, trapped sediments behind the sandbars that surround the Bandsar are rich in organic matter comprising crop residues and animal manure, which enhance soil fertility. Additionally, high porosity of the soil improves infiltration of the local soils, and such soils are good for growing wheat, barley, water melon and other crops (Sabzevar & Hasheminejhad, 2007, p. 448 – 449). 5.3 Public acceptance Both Qanats and Bandsars are highly preferred by many communities in Iran, which would ordinarily have high water deficits without these systems. The low cost of establishing Bandsars has particularly made them receive higher public acceptance over the years ((Taghvaee abrishmi 2007, p. 434). 6. Conclusion This report has presented and compared two methods of harvesting, managing and providing rainwater in Iran. Qanats are relatively more detailed in structure since they involve the use of groundwater – and are therefore less expensive than Bandsars which basically collect surface runoff. Both systems are sustainable and thus environmentally friendly although Qanats may lead to unsustainable use of water since they make the water constantly present; no notable environment impact is noted of the Bandsars. Both systems have received good public acceptance although the public acceptance of Bandsars is more pronounced because of the relatively lower cost of establishing this system. References English, P W n.d, ‘Qanats and lifeworlds in Iranian plateau villages’, Yale F&ES Bulletin 103, viewed 14 November 2012 Ghanbarpour, M R, Ahmadi, E & Gholami, S n.d, ‘Evaluation of different traditional water management systems in semi-arid regions (case study from Iran)’, viewed 14 November 2012 Pathak N & Heijnen H, n.d, ‘Rainwater harvesting and health aspects – working on WHO guidance’, viewed 14 November 2012 Sabzevar, AD & Hasheminejhad, Y 2007, ‘Bandsar, a successful story for flood agriculture in arid regions of Iran’, International History Seminar on Irrigation and Drainage Tehran-Iran May 2-5, 2007. Taghvaee abrishmi, A 2007, ‘Traditional water harvesting systems collections in Iran’, International History Seminar on Irrigation and Drainage Tehran-Iran May 2-5, 2007. Read More