کاریز یا قنات یا کهریز به راهی که در زیر زمین کنده شده تا آب از آن جریان یابد میگویند. کاریز کانالی است در عمق زمین برای ارتباط دادن رشته چاه هایی که از «مادر چاه» سرچشمه میگیردبه منظورهدایت آب به سطح زمین و مدیریّت آب برای کشاورزی و سایر مصارف. این کانال ممکن است تا رسیدن به سطح زمین هزارها متر به طول بیانجامد و سرانجام آب این کاریزها برای شرب و کشت و کار روی زمین میآیند که به این محل دهنه کاریز یا سر قنات می گویند.
طولانیترین کاریز جهان و عمیقترین مادر چاه در شهرستان گناباد با نام قنات قصبه قرار دارد که تاریخ کندن آن به دورهٔ هخامنشی و یا قبل از آن میرسد. ایرانیان باستان در چندین هزار سال قبل دست به این ابتکار جدید زده و آن را کاریز یا کهریز نام نهادند. با این اختراع که در نوع خود در جهان تا کنون بینظیر بودهاست، میتوان مقدار قابل توجهی از آبهای زیرزمینی را جمعآوری کرد و به سطح زمین رساند، که همانند چشمههای طبیعی، آب آن در تمام طول سال بدون هیچ ابزار کمکی از درون زمین به سطح زمین جاری می گردد تا زراعت و سرسبزی و باغ های میوه را به همراه آورد. کاریز که توسط کندی کاران مقنیان ایرانی اختراع شده، هزاران سال قدمت دارد. این حرفه به همراه خود ساعت آبی و آسیاب آبی را نیز به همراه آورده است قدمت بسیاری از کاریزهای ایران، از پنج-شش هزار سال متجاوز است و عمری برابر با تاریخ کهن ایران دارد. با وجود این که چندبن هزار سال از اختراع آن میگذرد، با این وجود هنوز هم این روش استفاده از آب، در قسمت مهمی از روستاها و مناطق مسکونی و کشاورزی و دامداری کشور معمول و متداول است و حتی رکن اصلی کشت و زرع در نواحی خشک است. این اختراع که امروزه شهرت جهانی پیدا کرده، بعدها از ایران به بسیاری از کشورهای جهان انتقال یافته و مورد استفادهٔ مردم در دیگر نقاط دنیا قرار گرفتهاست. البته گوبلو معتقد است که کاریز، ابتدا یک فن ویژه آبیاری نبوده، بلکه به طور کامل از تکنیک معدن نشأت گرفته و منظور از احداث آن جمعآوری آبهای زیرزمینی مزاحم (هرزه آبها) به هنگام حفر معادن بودهاست!؛؛. اگرچه در گسترهٔ فرهنگی ایران، از معادن «مس» و احتمالاً «روی» موجود در کوههای زاگرس، در هزارهٔ دوم قبل از میلاد مسیح بهرهبرداری شدهاست اما این نظر گوبلوچندان علمی بنظر نمی آیدو با مطالعات میدانی ما در مورد قناتهای ایران همخوانی ندارد.. .
کاریز، از یک دهانه یا هرنج که روباز است و یک کانال طولی شیب دار زیرزمینی تشکیل شده و چندین چاه عمودی که کانال زیر زمینی سرانجام به سطح زمین مرتبط میسازد، چاهها- که به آنها در موقع حفر، میله هم گفته میشود- علاوه بر کاربرد برای انتقال مواد حفاری شده به روی زمین، عمل تهویه کانال زیرزمینی را نیز انجام میدهند و راه ارتباطی برای لایروبی، تعمیر و بازدید از داخل کاریز نیز به شمار میروند.. به محل خروج آب قنات مظهر نیز میگویند.
آغاز کاریز همان دهانه کاریز است که «مظهر کاریز» نیز نامیده میشود. مظهر کاریز جایی است که آب از دل کاریز بیرون میآید و ظاهر میشود و میتواند برای آبیاری و دیگر مصارف مورد استفاده قرار بگیرد. قسمت انتهایی کاریز، «پیشکار کاریز» نامیده میشود که در آخرین قسمت آن، چاه مادر کاریز قرار گرفتهاست. قسمتهایی از کاریز که با حفر آنها هنوز آب بیرون نمیآید «خشکه کار» و قسمتی که آبدار است (قسمت انتهایی) قسمت «آبده کاریز» نامیده میشوند.
کندن کاریز معمولاً از مظهر آن که همان سطح زمین خشک است، شروع و به مناطق آبده چاه مادر، ختم میشود. بنابراین، اول دهانه کاریز یا هرنج که خشک است و بعداز آن اولین چاهها یا میلهها -که اینها هم خشک است و آب ندارند و به اصطلاح قسمت خشک کار کاریز نامیده میشوند، حفر میشوند. بعد کار به طرف قسمت بالادست که همان قسمتهای آبده و بیشتر آبده زمین میباشند، ادامه پیدا میکند.
طول و عمق کاریز[ویرایش]
طول یک رشته کاریز - که در میزان آبدهی آن نیز موثر است - نسبت به شرایط طبیعی متفاوت است. این شرایط بستگی به شیب زمین و عمق چاه مادر دارد. از طرف دیگر هر چه سطح آب زیرزمینی پایینتر باشد، عمق چاه مادر بیشتر میشود. طویلترین کاریزی که تا کنون در ایران حفر شده، در حوالی گناباد از توابع خراسان است که ۷۰ کیلومتر طول آن است و عمیقترین چاه مادر کاریزهای ایران به روایتی ۴۰۰ متر و به روایت دیگر ۳۵۰ متر عمق دارد و آن مربوط به کاریز «قصبه» گناباد است. مهمترین عاملی که طول کاریز را مشخص میکند، شیب زمین میباشد. هرچه شیب زمین کمتر باشد طول کاریز بیشتر و هرچه شیب بیشتر باشد طول کاریز کمتر خواهد بود.
از ابتدای اختراع قنات، تقسیم آب بین سهامداران توسط میرآب و با ساعت آبی یا فنجان انجام می شده است.
فنجان عبارت است از یک کاسه کوچک با سوراخی در وسط آن و چند درجه با علامت در بدنه داخلی آن که بر روی آبهای یک دیگ بزرگ قرار می گیرد. مانند تصویر(فنجان قنات زیبد گناباد)
ساعت آبی . .
طریقهٔ کار فنجان یا ساعت بدین گونه بوده که میر آب با چشم دوختن به فنجان با هر بار پرشدن و غرقشدن آن و خوردن کاسه به کف دیگ یک فنجان یا هفت دنگ و نیم یا (۷ دقیقه و نیم امروزی) محاسبه نموده و یک سنک کوچک برای هر بار غرقشدن کاسه در یک کیسه یا یک ظرف سفالی میگذاشته است. تا تعداد فنجانها و زمانی که سهامدار قنات آب براب باغ خود یا زمین میبرده را دقیقاً حساب کند مثلاً اگر ۱۰ سنگ درون کیسه باشد یعنی ۱۰ فنجان یا معادل امروزی ۷۵ دقیقه آب قنات را فرد استفاده کردهاست. اگر فردی ۱۰ فنجان سهم از قنات داشته باید (معادل امروزی هفتاد و پنج دقیقه) یعنی مدت زمانی که ۱۰ فنجان آب پر شود آب قنات را به زمین یا باغ خود رها میکرده است و با اعلام جار زدن و یا شیپور زدن یا یک صدای قراردادی فرد بعدی آب را به باغ یا زمین خود منتقل میکرده و به همین ترتیب... معمولاً محل استقرار دایمی فنجان و مدیر آن (میر آب) خانه فنجان بوده است. اما در فصل تابستان گاهی ممکن است فنجان را به محل اصلی تقسیم آب ببرند. کالیستنس مورخ یونانی که در لشکرکشی اسکندر مقدونی به ایران همراه او بود و رویدادهای روز و مشاهداتش را به طور منظم یادداشت میکرد در یادداشتی که بعداً با محاسبات تقویمی معلوم شده که متعلق به سپتامبر ۳۲۸ پیش از میلاد است نوشته است: در اینجا (ایران)، در دهکدهها که آب را بر حسب نوبت به کشاورزان برای زراعت میدهند، یک فرد از میان آنان (کشاورزان) انتخاب میشود تا بر زمان نوبت (و تقسیم زمانی سهام) نظارت داشته باشد. این فرد در کنار مجرای اصلی آب و محل انشعاب آن میان کشاورزان، بر سکویی مینشیند و ظرفی فلزی را که سوراخ بسیار ریزی در آن تعبیه شده است در ظرفی بزرگتر و پر از آب قرار میدهد که پس از پر شدن ظرف کوچک (یک بار و یا چند بار) که به آهستگی و طبق محاسبه قبلی ابعاد سوراخ آن صورت میگیرد، آب را قطع و آن را به جوی کشاورز دیگر باز میکند و این کار دائمی است و این وسیله (ساعت آبی) عدالت را برقرار کرده و از نزاع کشاورزان بر سر آب مانع میشود. . .
قنات دو طبقه[ویرایش]
تنها قنات دو طبقه جهان قنات دوطبقه مون اردستان در محله مون یکی از محلات شهرستان اردستان در استان اصفهان واقع است. این قنات در این محله شامل دو طبقهاست که که در هر طبقه آن آبی مسقل جریان دارد جالب این جاست که آب هیچ یک به دیگری نفوذ نمیکند این قنات ۸۰۰ سال پیش احداث شدهاست.
سیستم استخراج در کاریز طوری است که آب بدون کمک و صرف هزینه فقط با استفاده از نیروی ثقل از زمین خارج میگردد. با توجه به چاهها و کاریزهای موجود، آب کاریز در مقابل آبی که از چاه استخراج میشود، ارزانتر تمام میشود. آب کاریز دائمی است و در مواقع اضطراری کشت و زراعت و در مواقع حساس(نیاز به آب)، قطع نمیشود. منابع آب زیر زمینی توسط کاریز دیر تمام میشوند و استفاده طولانی دارند، هر چند به طور دائم آبها - چه مصرف شوند و چه نشوند - خارج میگردند. کاریز دارای مزایای بسیار زیادی است که در اینجا فقط به تعداد محدودی از آنها اشاره شدهاست.
در زمینهای هموار و نواحیای که زمین شیب کافی ندارد و نیز زمینهای خیلی سست و ماسهای امکان حفر کاریز نیست. آب کاریز، به طور دائم جریان دارد و قابل کنترل نیست. به همین خاطر کاریز مدام باعث تخلیه آب زیرزمینی میشود. در فصولی که به آب احتیاج نیست و یا احتیاج به آب خیلی کم است، امکان جلوگیری از جریان و یا کنترل کاریز وجود ندارد.
کاریز به خاطر این که در سفرههای آب زیرزمینی کم عمق استفاده میشود و این منابع هم غنی نیستند و دارای نوسان زیادی هستند، نسبت به تغییرات سطح آب زیر زمینی خیلی حساسیت دارد. در فصول گرم که گیاه به آب بیشتری نیاز دارد و همین طور در فصول و سالهای خشک، آب کاریز کم میشود. کاریز نسبت به چاه در مقابل سیل و زلزله و امثال اینها آسیب پذیرتر است و خرابی در کاریزها بعضی مواقع طوری است که احیا مجدد آنها یا ممکن نمیباشد و یا از لحاظ اقتصادی مقرون به صرفه نیست.[نیازمند منبع]
واژهٔ کاریز واژهای فارسی است و در اصل کهریز و شاید کهن ریز بودهاست. واژهٔ قنات کلمهٔ پارسی معرب شدهاست. در ایران خاوری و افغانستان و آسیای میانه واژهٔ کاریز بیشتر کاربرد دارد و در ایران باختری واژهٔ قنات. قنات خود عربی شدهٔ کنات فارسی است که از ریشهٔ فعل کندن گرفته شده است. /لینک مرده/ جمع «قنات» را «قنوات» گویند.
یخچال یک نوع آب انبار است که برای داشتن آب خنک در تابستان استفاده می شده است.این تکنیک در ایران قدمت بسیار زیادی داردآب انبارها و یخچالهایی که هم اکنون باقی مانده اند عموما مربوط به دوره صفویه و قاجار هستند اما سابقه این یخچال ها در ایران به دوره قبل از اسلام می رسد. در زمستانها آب انبار را از آب یخ و برف پر می کردند و در تابستان از آن استفاده می کردند.تا یکصد سال قبل بیشتر از هزار یخچال در شهرهای کویری ایران وجود داشته است.
فهرست منابع و مآخذ[ویرایش]
"Falaj" redirects here. For other uses, see Falaj (disambiguation).
"Karez" redirects here. For settlements in Aghanistan and Iran, see Kariz.
For other uses, see Qanat (disambiguation).
A qanāt (Arabic: قناة, Persian: قنات) is one of a series of well-like vertical shafts, connected by gently sloping tunnels. Qanāts create a reliable supply of water for human settlements and irrigation in hot, arid, and semi-arid climates.
The value of the qanat is directly related to the quality, volume, and regularity of the water flow. Much of the population of Iran and other arid countries in Asia and North Africa historically depended upon the water from qanats; the areas of population corresponded closely to the areas where qanats are possible. Although a qanat was expensive to construct, its long-term value to the community, and thereby to the group that invested in building and maintaining it, was substantial.
Qanats are also called kārīz (or kārēz from Persian: كاريز) (Iran, Afghanistan, Pakistan and Central Asia, derived from Persian: كاهریز), kahan (from Persian: کهن), kahriz/kəhriz (Azerbaijan); khettara (Morocco); galería (Spain); falaj (United Arab Emirates and Oman); Kahn (Baloch) or foggara/fughara (North Africa). Alternative terms for qanats in Asia and North Africa are kakuriz, chin-avulz, and mayun. Common variants of qanat in English include kanat, khanat, kunut, kona, konait, ghanat, ghundat.
Qanats are constructed as a series of well-like vertical shafts, connected by gently sloping tunnels. Qanats tap into subterranean water in a manner that efficiently delivers large quantities of water to the surface without need for pumping. The water drains by gravity, with the destination lower than the source, which is typically an upland aquifer. Qanats allow water to be transported over long distances in hot dry climates without loss of much of the water to evaporation.
It is very common in the construction of a qanat for the water source to be found below ground at the foot of a range of foothills of mountains, where the water table is closest to the surface. From this point, the slope of the qanat is maintained closer to level than the surface above, until the water finally flows out of the qanat above ground. To reach an aquifer, qanats must often extend for long distances.
Qanats are sometimes split into an underground distribution network of smaller canals called kariz. Like qanats, these smaller canals are below ground to avoid contamination. In some cases water from a qanat is stored in a reservoir, typically with night flow stored for daytime use. An Ab Anbar is an example of a traditional qanat-fed reservoir for drinking water in Persian antiquity.
The qanat system has the advantage of being resistant to natural disasters such as earthquakes and floods, and to deliberate destruction in war. Furthermore, it is almost insensitive to the levels of precipitation, delivering a flow with only gradual variations from wet to dry years.
Features common to regions that use qanat technology
The qanat technology is used most extensively in areas with the following characteristics:
Impact of qanats on settlement patterns
A typical town or city in Iran, and elsewhere where the qanat is used, has more than one qanat. Fields and gardens are located both over the qanats a short distance before they emerge from the ground and below the surface outlet. Water from the qanats defines both the social regions in the city and the layout of the city.
The water is freshest, cleanest, and coolest in the upper reaches and more prosperous people live at the outlet or immediately upstream of the outlet. When the qanat is still below grade, the water is drawn to the surface via water wells or animal driven Persian wells. Private subterranean reservoirs could supply houses and buildings for domestic use and garden irrigation as well. Further, air flow from the qanat is used to cool an underground summer room (shabestan) found in many older houses and buildings.
Downstream of the outlet, the water runs through surface canals called jubs (jūbs) which run downhill, with lateral branches to carry water to the neighborhood, gardens and fields. The streets normally parallel the jubs and their lateral branches. As a result, the cities and towns are oriented consistent with the gradient of the land; this is a practical response to efficient water distribution over varying terrain.
The lower reaches of the canals are less desirable for both residences and agriculture. The water grows progressively more polluted as it passes downstream. In dry years the lower reaches are the most likely to see substantial reductions in flow.
Traditionally qanats are built by a group of skilled laborers, muqannīs, with hand labor. The profession historically paid well and was typically handed down from father to son.
The critical, initial step in qanat construction is identification of an appropriate water source. The search begins at the point where the alluvial fan meets the mountains or foothills; water is more abundant in the mountains because of orographic lifting and excavation in the alluvial fan is relatively easy. The muqannīs follow the track of the main water courses coming from the mountains or foothills to identify evidence of subsurface water such as deep-rooted vegetation or seasonal seeps. A trial well is then dug to determine the location of the water table and determine whether a sufficient flow is available to justify construction. If these prerequisites are met, the route is laid out aboveground.
Equipment must be assembled. The equipment is straightforward: containers (usually leather bags), ropes, reels to raise the container to the surface at the shaft head, hatchets and shovels for excavation, lights, spirit levels or plumb bobs and string. Depending upon the soil type, qanat liners (usually fired clay hoops) may also be required.
Although the construction methods are simple, the construction of a qanat requires a detailed understanding of subterranean geology and a degree of engineering sophistication. The gradient of the qanat must be carefully controlled: too shallow a gradient yields no flow and too steep a gradient will result in excessive erosion, collapsing the qanat. And misreading the soil conditions leads to collapses, which at best require extensive rework and at worst are fatal for the crew.
Construction of a qanat is usually performed by a crew of 3-4 muqannīs. For a shallow qanat, one worker typically digs the horizontal shaft, one raises the excavated earth from the shaft and one distributes the excavated earth at the top.
The crew typically begins from the destination to which the water will be delivered into the soil and works toward the source (the test well). Vertical shafts are excavated along the route, separated at a distance of 20–35 m. The separation of the shafts is a balance between the amount of work required to excavate them and the amount of effort required to excavate the space between them, as well as the ultimate maintenance effort. In general, the shallower the qanat, the closer the vertical shafts. If the qanat is long, excavation may begin from both ends at once. Tributary channels are sometimes also constructed to supplement the water flow.
Most qanats in Iran run less than 5 km, while some have been measured at ~70 km in length near Kerman. The vertical shafts usually range from 20 to 200 meters in depth, although qanats in the province of Khorasan have been recorded with vertical shafts of up to 275 m. The vertical shafts support construction and maintenance of the underground channel as well as air interchange. Deep shafts require intermediate platforms to simplify the process of removing spoil.
The construction speed depends on the depth and nature of the ground. If the earth is soft and easy to work, at 20 meters depth a crew of four workers can excavate a horizontal length of 40 meters per day. When the vertical shaft reaches 40 meters, they can excavate only 20 meters horizontally per day and at 60 meters in depth this drops below 5 horizontal meters per day. In Algeria, a common speed is just 2 m per day at 15 m depth. Deep, long qanats (which many are) require years and even decades to construct.
The excavated material is usually transported by means of leather bags up the vertical shafts. It is mounded around the vertical shaft exit, providing a barrier that prevents windblown or rain driven debris from entering the shafts. These mounds may be covered to provide further protection to the qanat. From the air, these shafts look like a string of bomb craters.
The qanat's water-carrying channel must have a sufficient downward slope that water flows easily. However the downward gradient must not be so great as to create conditions under which the water transitions between supercritical and subcritical flow; if this occurs, the waves that result can result in severe erosion that can damage or destroy the qanat. In shorter qanats the downward gradient varies between 1:1000 and 1:1500, while in longer qanats it may be almost horizontal. Such precision is routinely obtained with a spirit level and string.
In cases where the gradient is steeper, underground waterfalls may be constructed with appropriate design features (usually linings) to absorb the energy with minimal erosion. In some cases the water power has been harnessed to drive underground mills. If it is not possible to bring the outlet of the qanat out near the settlement, it is necessary to run a jub or canal overground. This is avoided when possible to limit pollution, warming and water loss due to evaporation.
The Persians were using water clocks in 328 BC to ensure a just and exact distribution of water from qanats to their shareholders for agricultural irrigation. The use of water clocks in Iran, especially in Zeebad, dates back to 500 BC. Later they were also used to determine the exact holy days of pre-Islamic religions, such as the Yaldā (winter solstice), Tiregān (mid-summer) or Nowruz (spring equinox) - the shortest, longest, and equal-length days and nights of the years. The water clocks used in Iran were one of the most practical ancient tools for timing the yearly calendar. Water clocks, or Fenjaan, in Persia reached a level of accuracy comparable to today's standards of timekeeping. The fenjaan was the most accurate and commonly used timekeeping device for calculating the amount or the time that a farmer must take water from a qanat or well for irrigation, until it was replaced by more accurate current clocks. Persian water clocks were a practical and useful tool for the qanat's shareholders to calculate the length of time they could divert water to their farms. The qanat was the only water source for agriculture and irrigation, so that a just and fair water distribution was very important. Accordingly a fair and astute elder was elected to be the manager of the water clock, and at least two full-time managers were needed to control and observe the number of fenjaans and announce the exact time during the days and nights.
The fenjaan was a big pot full of water and a bowl with small hole in the center. When the bowl become full of water, it would sink into the pot, and the manager would empty the bowl and again put it on the top of the water in the pot. He would record the number of times the bowl sank by putting small stones into a jar.
The place where the clock was situated, and its managers, were collectively known as khaneh fenjaan. Usually this would be the top floor of a public house, with west- and east-facing windows to show the time of sunset and sunrise. There was also another time-keeping tool named a staryab or astrolabe, but it was mostly used for superstitious beliefs and was not practical for use as a farmers' calendar. The Zeebad Gonabad water clock was in use until 1965, when it was substituted by modern clocks.
The vertical shafts may be covered to minimize blown-in sand. The channels of qanats must be periodically inspected for erosion or cave-ins, cleaned of sand and mud and otherwise repaired. For safety, air flow must be assured before entry.
Some damaged qanats have been restored. To be sustainable, restoration needs to take into account many nontechnical factors beginning with the process of selecting the qanat to be restored. In Syria, three sites were chosen based on a national inventory conducted in 2001. One of them, the Drasiah qanat of Dmeir, was completed in 2002. Selection criteria included the availability of a steady groundwater flow, social cohesion and willingness to contribute of the community using the qanat, and the existence of a functioning water-rights system.
Applications of qanats
Irrigation and drinking water supply
The primary applications of qanats are for irrigation, providing cattle with water, and drinking water supply. Other applications include cooling and ice storage.
Qanats used in conjunction with a wind tower can provide cooling as well as a water supply. A wind tower is a chimney-like structure positioned above the house; of its four openings, the one opposite the wind direction is opened to move air out of the house. Incoming air is pulled from a qanat below the house. The air flow across the vertical shaft opening creates a lower pressure (see Bernoulli effect) and draws cool air up from the qanat tunnel, mixing with it. The air from the qanat is drawn into the tunnel at some distance away and is cooled both by contact with the cool tunnel walls/water and by the transfer of latent heat of evaporation as water evaporates into the air stream. In dry desert climates this can result in a greater than 15°C reduction in the air temperature coming from the qanat; the mixed air still feels dry, so the basement is cool and only comfortably moist (not damp). Wind tower and qanat cooling have been used in desert climates for over 1000 years.
The ice could be brought in during the winters from nearby mountains. But in a more usual and sophisticated method they built a wall in the east–west direction near the yakhchal (ice pit). In winter, the qanat water would be channeled to the north side of the wall, whose shade made the water freeze more quickly, increasing the ice formed per winter day. Then the ice was stored in yakhchals — specially designed, naturally cooled refrigerators. A large underground space with thick insulated walls was connected to a qanat, and a system of windcatchers or wind towers was used to draw cool subterranean air up from the qanat to maintain temperatures inside the space at low levels, even during hot summer days. As a result, the ice melted slowly and was available year-round.
Qanats by country
The Qanats are called Kariz in Dari (Persian) and Pashto and have been in use since the pre-Islamic period. It is estimated that more than 20,000 Karizes were in use in the 20th century. The oldest functional Kariz which is more than 300 years old and 8 kilometers long is located in Wardak province and is still providing water to nearly 3000 people. The incessant war for the last 30 years has destroyed a number of these ancient structures. In these troubled times maintenance has not always been possible. To add to the troubles, as of 2008 the cost of labour has become very high and maintaining the Kariz structures is no longer possible.[dubious ] Lack of skilled artisans who have the traditional knowledge also poses difficulties. A number of the large farmers are abandoning their Kariz which has been in their families sometimes for centuries, and moving to tube and dug wells backed by diesel pumps.
However, the government of Afghanistan is aware of the importance of these structures and all efforts are being made to repair, reconstruct and maintain (through the community) the kariz. The Ministry of Rural Rehabilitation and Development along with National and International NGOs is making the effort.
There are still functional qanat systems in 2009. American forces are reported to have unintentionally destroyed some of the channels during expansion of a military base, creating tensions between them and the local community. Some of these tunnels have been used to store supplies, and to move men and equipment underground.
Main article: Turpan water system
The oasis of Turpan, in the deserts of Xinjiang in northwestern China, uses water provided by qanat (locally called karez). The number of karez systems in the area is slightly below 1,000, and the total length of the canals is about 5,000 kilometers.
Turpan has long been the center of a fertile oasis and an important trade center along the Silk Road's northern route, at which time it was adjacent to the kingdoms of Korla and Karashahr to the southwest. The historical record of the karez extends back to the Han Dynasty. The Turfan Water Museum is a Protected Area of the People's Republic of China because of the importance of the Turpan karez water system to the history of the area.
There are karez (qanat) systems in Gulburga, Bidar and Burhanpur (Kundi Bhandara) as well. The system in Bidar with 21 vertical shafts is said to extend for about two kilometers, with 21 vertical shafts, of which a few have been closed by builders and developers, leaving 17 visible today. The karez vertical shafts are used by farmers and neighborhood settlements. The Indian Heritage Cities Network Foundation (IHCNF) has been working towards conservation of the Karez system. During its survey, IHCNF also discovered a royal bath (Bagh-e-Hammam) probably of the Bahmani period. Local knowledge claims the presence of a terra cotta pipe from the karez mouth to Bagh-e-Hammam.
In the middle of the twentieth century, an estimated 50,000 qanats were in use in Iran, each commissioned and maintained by local users. Of these, only 25,000 remain in use as of 1980.
One of the oldest and largest known qanats is in the Iranian city of Gonabad, and after 2,700 years still provides drinking and agricultural water to nearly 40,000 people. Its main well depth is more than 360 meters and its length is 45 kilometers. Yazd, Khorasan and Kerman are zones for known for their dependence on an extensive system of qanats.
In traditional Persian architecture, a Kariz (کاریز) is a small Qanat, usually within a network inside an urban setting. The Kariz is the structure that distributes a qanat to its final destinations.
A survey of qanat systems in the Kurdistan region of Iraq conducted by the Department of Geography at Oklahoma State University (USA) on behalf of UNESCO in 2009 found that out of 683 karez systems, some 380 were still active in 2004, but only 116 in 2009. Reasons for the decline of qanats include "abandonment and neglect" prior to 2004, "excessive pumping from wells" and, since 2005, drought. Water shortages are said to have forced, since 2005, over 100,000 people who depended for their livelihoods on karez systems to leave their homes. The study says that a single karez has the potential to provide enough household water for nearly 9,000 individuals and irrigate over 200 hectares of farmland. UNESCO and the government of Iraq plan to rehabilitate the karez through a Karez Initiative for Community Revitalization to be launched in 2010. Most of the karez are in Sulaymaniyah Governorate (84%). A large number are also found in Erbil Governorate (13%), especially on the broad plain around and in Erbil city.
Among the qanats built in the Roman Empire, the 94 km long Gadara Aqueduct in northern Jordan was possibly the longest continuous qanat ever built. Partly following the course of an older Hellenistic aqueduct, excavation work arguably started after a visit by emperor Hadrian in 129-130 AD. The Gadara Aqueduct was never quite finished and was put in service only in sections.
The Chagai district is in the north west corner of Balochistan, Pakistan, bordering with Afghanistan and Iran. Qanats, locally known as karezes, are found more broadly in this region. They are spread from Chaghai district all the way up to Zhob district. A number of them are present in Qilla Abdullah and Pishin districts. Karezes are also extensively found in the neighbouring areas of Afghanistan such as Kandahar. The remains of karezes found in different parts of the district are attributed to the Arabs.
Qanats were found over much of Syria. The widespread installation of groundwater pumps has lowered the water table and qanat system. Qanats have gone dry and been abandoned across the country.
In Oman from the Iron Age Period (found in Salut, Bat and other sites) a system of underground aqueducts called Falaj were constructed, a series of well-like vertical shafts, connected by gently sloping horizontal tunnels. There are three types of Falaj: Daudi (داوودية) with underground aqueducts, Ghaili (الغيلية) requiring a dam to collect the water, and Aini (العينية) whose source is a water spring. These enabled large scale agriculture to flourish in a dryland environment. According to UNESCO, some 3,000 aflaj (plural) or falaj (singular), are still in use in Oman today. Nizwa, the former capital city of Oman, was built around a falaj which is in use to this day. These systems date to before the Iron Age in Oman. In July 2006, five representative examples of this irrigation system were inscribed as a World Heritage Site.
United Arab Emirates
There are four main oases in the Egyptian desert. The Kharga Oasis is one that has been extensively studied. There is evidence that as early as the second half of the 5th century BC water brought in qanats was being used. The qanats were excavated through water-bearing sandstone rock, which seeps into the channel, with water collected in a basin behind a small dam at the end. The width is approximately 60 cm, but the height ranges from 5 to 9 meters; it is likely that the qanat was deepened to enhance seepage when the water table dropped (as is also seen in Iran). From there the water was used to irrigate fields.
There is another instructive structure located at the Kharga oasis. A well that apparently dried up was improved by driving a side shaft through the easily penetrated sandstone (presumably in the direction of greatest water seepage) into the hill of Ayn-Manâwîr to allow collection of additional water. After this side shaft had been extended, another vertical shaft was driven to intersect the side shaft. Side chambers were built, and holes bored into the rock — presumably at points where water seeped from the rocks — are evident.
David Mattingly reports foggara extending for hundreds of miles in the Garamantes area near Jarma in Libya: "The channels were generally very narrow - less than 2 feet wide and 5 high - but some were several miles long, and in total some 600 foggara extended for hundreds of miles underground. The channels were dug out and maintained using a series of regularly spaced vertical shafts, one every 30 feet or so, 100,000 in total, averaging 30 feet in depth, but sometimes reaching 130."
The foggara water management system in Tunisia, used to create oases, is similar to that of the Iranian qanat. The foggara is dug into the foothills of a fairly steep mountain range such as the eastern ranges of the Atlas mountains. Rainfall in the mountains enters the aquifer and moves toward the Saharan region to the south. The foggara, 1 to 3 km in length, penetrates the aquifer and collects water. Families maintain the foggara and own the land it irrigates over a ten-meter width, with width reckoned by the size of plot that the available water will irrigate.
Qanats (designated foggaras in Algeria) are the source of water for irrigation in large oases like that at Gourara. The foggaras are also found at Touat (an area of Adrar 200 km from Gourara). The length of the foggaras in this region is estimated to be thousands of kilometers.
Although sources suggest that the foggaras may have been in use as early as 200 AD, they were clearly in use by the 11th century after the Arabs took possession of the oases in the 10th century and the residents embraced Islam.
The water is metered to the various users through the use of distribution weirs that meter flow to the various canals, each for a separate user.
The humidity of the oases is also used to supplement the water supply to the foggara. The temperature gradient in the vertical shafts causes air to rise by natural convection, causing a draft to enter the foggara. The moist air of the agricultural area is drawn into the foggara in the opposite direction to the water run-off. In the foggara it condenses on the tunnel walls and the air passes out of the vertical shafts. This condensed moisture is available for reuse.
In southern Morocco, the qanat (locally khettara) is also used. On the margins of the Sahara Desert, the isolated oases of the Draa River valley and Tafilalt have relied on qanat water for irrigation since the late 14th century. In Marrakech and the Haouz plain, the qanats have been abandoned since the early 1970s, having dried up. In the Tafilaft area, half of the 400 khettaras are still in use. The Hassan Adahkil Dam's impact on local water tables is said to be one of the many reasons for the loss of half of the khettara.
Qanats have been preserved in Armenia in the community of Shvanidzor, in the southern province of Syunik, bordering with Iran. Qanats are named kahrezes in Armenian. There are 5 kahrezes in Shvanidzor. Four of them were constructed in XII-XIVc, even before the village was founded. The fifth kahrez was constructed in 2005. Potable water runs through I, II and V kahrezs. Kahrez III and IV are in quite poor condition. In the summer, especially in July and August, the amount of water reaches its minimum, creating a critical situation in the water supply system. Still, kahrezes are the main source of potable and irrigation water for the community.
The territory of Azerbaijan was home to numerous kahrizes many centuries ago. Archaeological findings suggest that long before the ninth century AD, kahrizes by which the inhabitants brought potable and irrigation water to their settlements were in use in Azerbaijan. Traditionally, kahrizes were built and maintained by a group of masons called ‘Kankans’ with manual labour. The profession was handed down from father to son.
It is estimated that until the 20th century, nearly 1500 kahrizes, of which as many as 400 were in the Nakhichevan Autonomous Republic, existed in Azerbaijan. However, following the introduction of electric and fuel-pumped wells during Soviet times, kahrizes were neglected.
Today, it is estimated that 800 are still functioning in Azerbaijan. These operational kahrizes are key to the life of many communities.
International Organization for Migration and the Revival of Kahriz
In 1999, upon the request of the communities in Nakhichevan, taking into consideration the needs and priorities of the communities, especially women as the main beneficiaries, IOM began implementing a pilot programme to rehabilitate the kahrizes. By 2011 IOM rehabilitated more 143 kahrizes with funds from the United Nations Development Programme (UNDP), European Commission (EC), Canada International Development Agency (CIDA), Swiss Agency for Development and Cooperation (SDC) and the Bureau of Population, Refugees, and Migration, US State Department (BPRM) and the self-contribution of the local communities.
KOICA and IOM's Ongoing Kahriz Rehabilitation Project in Azerbaijan
In 2010, IOM began a kahriz rehabilitation project with funds from the Korea International Cooperation Agency (KOICA) which aims to fully renovate a total of 20 kahrizes in the mainland of Azerbaijan. Of these 20 kahrizes, already 16 have been rehabilitated and four are currently under rehabilitation. IOM will complete the works by the end of 2012.
The Tunnel of Eupalinos on Samos runs for 1 kilometre through a hill to supply water to the town of Pythagorion. It was built on the order of Polycrates around 550 BC. At either end of the tunnel proper, shallow qanat-like tunnels carried the water from the spring and to the town.
The 5,653 m long Claudius Tunnel, intended to drain the largest Italian inland water, Fucine Lake, was constructed using the qanat technique. It featured shafts up to 122 m deep. The entire ancient town of Palermo in Sicily was equipped with a huge qanat system built during the Arab period (827–1072). Many of the qanats are now mapped and some can be visited. The famous Scirocco room has an air-conditioning system cooled by the flow of water in a qanat and a "wind tower", a structure able to catch the wind and use it to draw the cooled air up into the room.
The Raschpëtzer near Helmsange in southern Luxembourg is a particularly well preserved example of a Roman qanat. It is probably the most extensive system of its kind north of the Alps. To date, some 330 m of the total tunnel length of 600 m have been explored. Thirteen of the 20 to 25 shafts have been investigated. The qanat appears to have provided water for a large Roman villa on the slopes of the Alzette valley. It was built during the Gallo-Roman period, probably around the year 150 and functioned for about 120 years thereafter.
There are still many examples of galeria or qanat systems in Spain, most likely brought to the area by the Moors during their occupation of the Iberian peninsula. Turrillas in Andalusia on the north facing slopes of the Sierra de Alhamilla has evidence of a qanat system. Granada is another site with an extensive qanat system.