ارزیابی حداقل جریان زیست محیطی رودخانه ها با روش های اکو- هیدرولوژیکی (مطالعه موردی: رودخانه باراندوزچای- حوضه دریاچه ارومیه)

نوع مقاله : مقالات پژوهشی

نویسندگان

دانشگاه ارومیه

چکیده

طرح های توسعه منابع آب (نظیر احداث سد ها) دارای اثرات زیست محیطی متعددی می باشد، که تغییر رژیم طبیعی رودخانه و کاهش جریان سطحی پایین دست از مهم ترین آن است. هدف اصلی از تحقیق حاضر، برآورد جریان زیست محیطی رودخانه باراندوزچای، ارومیه، از پنج روش هیدرولوژیکی (1- تنانت، 2- تسمن، 3- تحلیل منحنی تداوم جریان، 4- تغییر منحنی تداوم جریان، 5- مدل ذخیره رومیزی) بوده است. نتایج این تحقیق نشان می دهد که برای حفظ رودخانه باراندوزچای در حداقل وضعیت اکولوژیکی قابل قبول (کلاس مدیریت زیست محیطی C)، شدت جریان 9/1 متر مکعب بر ثانیه (معادل 26 درصد متوسط جریان سالانه) به‌طور متوسط در طول رودخانه تا دریاچه ارومیه، باید برقرار گردد.

کلیدواژه‌ها


عنوان مقاله [English]

Evaluation of Environmental Flows in Rivers Using Hydrological Methods (Case study: The Barandozchi River- Urmia Lake Basin)

نویسندگان [English]

  • S. Mostafavi
  • M. Yasi
Urmia University
چکیده [English]

Introduction Development of water resources projects are accompanied by several environmental impacts, among them, the changes in the natural flow regime and the reduction of downstream water flows. With respect to the water shortages and non-uniform distribution of rainfall, sustainable management of water resources would be inevitable. In order to prevent negative effects on long-term river ecosystems, it is necessary to preserve the ecological requirements of the river systems. The assessment of environmental flow requirements in a river ecosystem is a challenging practice all over the world, and in particular, in developing countries such as Iran. Environmental requirements of rivers are often defined as a suite of flow discharges of certain magnitude, timing, frequency and duration. These flows ensure a flow regime capable of sustaining a complex set of aquatic habitats and ecosystem processes and are referred to as "environmental flows". There are several methods for determining environmental flows. The majority of these methods can be grouped into four reasonably distinct categories, namely as: hydrological, hydraulic rating, habitat simulation (or rating), and holistic methodologies. However, the current knowledge of river ecology and existing data on the needs of aquatic habitats for water quantity and quality is very limited. It is considered that there is no unique and universal method to adapt to different rivers and/or different reaches in a river. The main aim of the present study was to provide with a framework to determine environmental flow requirements of a typical perennial river using eco-hydrological methods. The Barandozchi River was selected as an important water body in the Urmia Lake Basin, Iran. The preservation of the river lives, the restoration of the internationally recognized Urmia Lake, and the elimination of negative impact from the construction of the Barandoz dam on this river were the main concerns in this study.
Materials and Methods: With lack of ecological data, the environmental requirements of the Barandozchi River were investigated using five eco-hydrological methods (1- Tennant, 2- Tessman, 3- Flow Duration Indices, 4- FDC shifting, 5- DRM). Some of these methods are too simplistic and do not take into account the direct hydro-ecological interactions (e.g. Tennant method), and some have been developed for a specific country/region (e.g., DRM), and need to be adapted to a different physiographic environment before they can be reliably applied. Two ecological friendly models GEFC, and DRM were tested to estimate the environmental flow of this river. The results were compared with corresponding flows allocated for the release from the Barandoz Dam (currently under construction).
Results and Discussion: The prediction of the mean annual environmental flows from five eco-hydrological methods are presented and compared with the corresponding value reported in the downstream dam’s documents. The ultimate decision making based on the potential flows in the river, the environmental class of the river management, and engineering judgment is also recommended for the flows in the river towards the Urmia Lake. The results indicated that the flow allocation for the river environment (4% of mean annual flows) is not sufficient to meet the minimum flow requirements for any of the targeting species in the river ecosystem. In order to maintain the Barandozchi River at minimum acceptable environmental status (i.e. Class C of environmental management), an average annual flow of 1.9 m3/s (26% MAR) are to be provided. The distribution of monthly flow rates in the river is also recommended for sustaining the Barandozchi River life.
Conclusion: The provision for the minimum ecological flows was investigated in the Barandozchi River ecosystem. The results indicated that, in order to maintain the Barandozchi River at minimum acceptable environmental status (i.e. Class C), an average annual flow of 1.9 m3/s (26% MAR) are to be provided along the river towards the internationally recognized Urmia Lake, in Iran. Considering the construction of the Barandoz dam on this river, the pre-determined environmental flow releases from the dam are to be revised in order to increase the order of flows from 4% to 26% or more. Further investigation is necessary to take into account for the targeting riverine species and for the saving of the Urmia lake ecosystem. It is noted that minimum flow requirements are to be allocated in critical months of the year or during drought period of the river basin. Water leasing from agricultural users is an option or a necessary action whenever long-term environmental damages to the river ecosystem must be avoided.

کلیدواژه‌ها [English]

  • Environmental Flow
  • Eco-Hydro methods
  • Barandozchi River
  • Urmia Lake
1- Abkhan consulting engineering. 2009. Environmental report of Barandozchi Dam. West Azarbaijan Regional Water Company.
2- Dyson M., Bergkamp G., and Scanlon J. 2003. The essentials of environmental flows. Gland, Switzerland and Cambridge, UK, IUCN, 118 P.
3- Hughes D.A., and Munster F. 2000. Hydrological information and techniques to support the determination of the water quantity component of the ecological reserve for rivers. WRC Report 867/3/2000, Report to the Water Research Commission by the Institute for Water Research, Rhodes University, Pretoria, South Africa.
4- Hughes D.A., and Hannart P. 2003. A desktop model used to provide an initial estimate of the ecological instream flow requirements of rivers in South Africa. Journal of Hydrology, 270:167-181.
5- Kashaigili J.J., Mccartney M., and Mahoo H.F. 2007. Estimation of environmental flows in the Great Ruaha River Catchment, Tanzania. Journal of Physics and Chemistry of the Earth, 32:1007-1014.
6- Mazvimavi D., Madamombe E., and Makurira H. 2007. Assessment of environmental flow requirements for river basin planning in Zimbabwe. Journal of Physics and Chemistry of the Earth, 30:639-647.
7- Orth D.J., and Maughan O.E. 1981. Evaluation of the "Montana Method" for Recommending Instream Flows in Oklahoma Streams. Proceedings of the Oklahoma Academy of Science, 61:62-66.
8- Pyrce R. 2004. Hydrological low flow indices and their uses. WSC Report 4, Watershed Science Centre, Trent University, Peterborough, Ontario, 33 p.
9- Shokoohi A., and Behrooznia M. 2010. Evaluation of environmental flows in rivers using hydrological and hydraulic methods. 9th Iranian hydraulic conference, Tarbiat Modares university, Tehran. (in Persian)
10- Sima s. 2005. Integrated environmental management of current reservoirs. The thesis submitted for the degree of master of science, Department of Civil engineering, Sharif university of technology, Tehran. (in Persian with English abstract)
11- Smakhtin V.U. 2001. Low flow hydrology: a review. Journal of Hydrology, 240:147-186.
12- Smakhtin V.U., Revenga C., and Döll P. 2004. Taking into account environmental water requirements in global-scale water resources assessments. Research Report 2 of the CGIAR, International Water Management Institute, Colombo, Sri Lanka, 24 p.
13- Smakhtin V.U., and Anputhas M. 2006. An assessment of environmental flow requirements of Indian river basins. IWMI Research Report 10, International Water Management Institute, Colombo, Sri Lanka, 36 p.
14- Standard of Water and Wastewater industries. 2009. Guideline for finding aquatic ecosystems environmental water requirement. Ministry of energy,Office of deputy for Water and Wastewater affairs, Bureau of engineering and technical criterias for Water and Wastewater, 113 p.
15- Tennant D. L. 1976. Instream flow regimens for fish, wildlife, recreation and related environmental resources. Fisheries, 1:6-10.
16- Tessman S.A. 1980. Environmental Assessment, Technical Appendix E, in Environmental Use Sector Reconnaissance Elements of the Western Dakotas Region of South Dakota Study. Water Resources Research Institute, South Dakota State University, Brookings, SD.
17- Tharme R.E. 2003. A global perspective on environmental flow assessment: emerging trends in the development and application of environmental flow methodologies for rivers. River Research and Applications, 19:397-441.