تکوین ژئومرفولوژیک چاه نیمه ها

نویسندگان

1 دانشگاه اصفهان

2 دانشگاه زابل

چکیده

چند پدیدۀ ژئومرفیک منحصر بفرد در ایران وجود دارد که می­توان کلوت­ها و چاه­نیمه ها را در زمره آنها تلقی نمود. در مورد نحوه تکوین چاه نیمه ها در استان سیستان و بلوچستان در کتب و مقالات انتشار یافته دو نظریه وجود دارد که یکی تکوین آنها را به فعالیت های تکتونیکی و دیگری به فرایند آب و باد نسبت داده و هنوز در مورد ارزیابی دقیق تکوین آنها مطالعات مستندی در دسترس نیست و تنها به عباراتی کلی پسنده شده است. با توجه به ابهامات متعددی که در این زمینه وجود داشت طرحی برای تحقیق پیرامون نحوه تکوین این پدیده ژئومرفیک صورت گرفت. این طرح با کالبد شکافی محدوده های گستره این پدیده در ایران و افغانستان و با اتکا به روش تحلیل فرم و فرایند و بهره جستن از تکنیک سنجش ازدور به نتایج دیگری دست یافته است که حاصل آنرا میتوان بشرح زیر خلاصه نمود:

*پدیده چاه نیمه ها دارای 5 مدل گوناگون تکوینی است که تنها یک مدل آن تحت تاثیر فرسایش دیفرانسیل فیلیش های زاهدان و آن هم در ارتفاعات تکوین یافته و مابقی حاصل فرایند آب در محیط آبی و قاره­ایست.

*این پدیده نادر راهبرد عمومی ذخیره اب در منطقه را تعریف میکند و تنها جایگزین ذخیره سازی آب­های سطحی و زیر زمینی در ناحیه هامون است.

کلیدواژه‌ها


عنوان مقاله [English]

The geomorphologic development of Chahnimes

نویسندگان [English]

  • ehsan ataei kia 1
  • alireza shahbazi 2
  • mohamad hosain raamesht 1
1
2
چکیده [English]

Introduction
One of the relatively unique forms in Iran is the shallow closed and open pits which is so called “well half”. This phenomenon has been found and named in the eastern part of Iran and although some steps have been taken to utilize it, there is no precise information about its development except for general information which is kind of a guess. The well halves are the most important supply of water in Sistan plain, and big and heavily populated cities including Zahedan and Zabol. Regarding the subject of this study, two theories have been published in Persian sources. The first theory states that these well halves have been created on by the tectonic activities on Marni sediments. On the other hand, the other theory says that the well halves have been created by the aquatic erosion in the first phase and wind erosion in the second phase. This study aims to explain the creation and development of these well halves and the process causing This phenomenon.
Materials and Methods
The method used in this study is based on the form and process analysis and the feature of each pit was provided in database using graphical document, digital elevation data (DEM) and the identification of well halves and the calculation of level, volume, depth and the its balanced relation with each other. After tracking the effects of flow performance in this region and the changes in water level of Hamun Lake in Quaternary delay phase, the sequestration flow performance in open surrounding of lake and land were provided. The information on the performance of random flows in altitude and plain levels was observed and the erosion of differential in the places of flysch formation in Zahedan and the development of pits were modeled.
Discussion and Results
The conducted field studies and observations in this region make some considerable points clear. Based on the identification of the sediment streams of flows, the entrance and crossing these streams into the lake are clearly seen. Generally, the major entrance streams into the lake can be divided into 3 parts including the eastern and northern parts.
These 3 major sediment streams create the grounds for the involvement the sediment in the aquatic environment of Hamun and the major ground of most developmental models of such well halves begin from this process. Thus, the development process of well halves can specifically explained as the following:
The development of well halves is achieved mostly due to the aquatic flows and sediment on the floor of Hamun.
Although the well halves have been created in the aquatic process, they do not have the single model and based on the conducted studies and the field operation and the analysis of satellite images and a flight over the region, five different outstanding models were graphically modelled.
Among five identified models, one of them is researching model and other 4 models are erosive. In other words, just one of the five models seen in the mountainous heights has been produced by relative erosion in the sediment called Zahedan’s flysch and other four models have been formed in deltaic sediments on entrance of Hamun Lake.
Regarding five developmental models, the manageable group of pits consists of 11 pits, four of which including number 1, 2, 3, and 4 have been organized, flooded and used. Concerning the conducted studies, the amount of water that can be stored in these pits is 1900000000 cm. In addition, in order to connect the probable water stored in these pits, it is essential to review the possibility of making connection system among pits. Thus, after the geometric and topographic surveys of a system, the connection among pits was provided.
Conclusions
Regarding the conducted studies, it became clear that the well halves have five developmental models, one of which is researching model and other 4 models are erosive. In other words, just one of the five models seen in the mountainous heights has been produced by relative erosion in the sediment called Zahedan’s flysch and other four models have been formed in deltaic sediments on entrance of Hamun Lake. Thus, the phases of development and creation of well halves can be regarded as erosive phenomena that four models of its development have been exactly created from different volume of sediment in Hamun Lake and deltaic sediments of Hamund River. Based on the arguments it can be concluded the well halves that is solely an aquatic process (river, delta, lake, and relative erosion) have created special phenomenon called natural store of water in the region. Regarding the needed amount of water in this region (population: 1400000), 1800000000, that has been provided by Water Organization, it can be understood that the current nature-made pits in this region can supply the residents with the needed water. It is evident that the total amount of water from Hamun water basin is 36 billion cm and although the considerable part of rainfall evaporates, storing 1900000000 cm in well halves is feasible and it indicates that there is enough amount of money in the region.

کلیدواژه‌ها [English]

  • well half
  • form and process analysis
  • erosion of differential
  • Hamun
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