@article { author = {Yarahmadi, Dariush}, title = {Hydroclimatology Analysis of Water Level Fluctuations in Urmia Lake}, journal = {Physical Geography Research}, volume = {46}, number = {1}, pages = {77-92}, year = {2014}, publisher = {University of Tehran}, issn = {2008-630X}, eissn = {2423-7760}, doi = {10.22059/jphgr.2014.50620}, abstract = {IntroductionLake Urmia, at the northwestern tip of Iran, is one of the largest permanent hyper saline lakes inthe world and the largest lake in the Middle East. The lake is located between EasternAzerbaijan and Western Azerbaijan, west of the southern portion of the similarly shapedCaspian Sea. It extends as much as 140km from north to south and is as wide as 85km from eastto west during high water level periods. Because of being located in a dry and semi-dry region,this region doesn’t have suitable water resources comparing with global average waterresources. Drought, climatic fluctuations, and shortage and disorder of rainfall cause manyproblems with regard to food and water for people who live in this region. Urmia lake is alsoone the most important and the largest aquatic ecosystems of Iran. The systemic and chainchanges in the lake will lead to great effects on the climate and economic, social and hydrologyconditions. Oscillations of the lake water levels and volume in recent years have attracted manyopinions and created apprehensions.MethodologyGroundwater data, meteorological precipitation and temperature data were obtained from Urmiastation of Meteorology Organization for the period from 1981 to 2010. Then time series wereformed for temperature and precipitation in the form of annual, seasonal, and monthly files. Thetime series of temperature, precipitation, rivers discharges, and water table levels andoscillations of the lake water level were collected and adjusted for the periods 1981-2010. Toinform homogeneity and randomness of data and possibility of any trends in the time series, thenonparametric test was used. In this study, precipitation, river discharges and water tables and􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯􀀯∗E-mail: d.yarahmadi@gmail.com Tel: +98 916165428114 Physical Geography Research Quarterly, 46 (1), Spring 2014temperatures were assessed as the independent variable and the water level as the dependentvariable. After reviewing the different parametric and nonparametric tests on the data in thisstudy, we eventually used a multivariable regression parametric test (Y=a+b1x1+b2x2) fortemperature and precipitation and these tests ultimately showed the ability to cover the analysisof data and review of this study.To determine the direction of the trend, type and time of changes based on a Man-Kendallgraphical and statistical test, the following formulas were used:􀜷􀝅 􀵌􁈺􀀃􀏃 􀀃􀝐􀝅 􀵆 􀀃􀜧􀝅 􁈻􀎾􀀙􀂋1)􀜷´􀝅 􀵌􀵆􁈺􀀃􀏃 􀀃􀝐´􀝅 􀵆 􀀃􀜧´􀝅􀀃􁈻􀎾􀀙´􀂋2)Results and DiscussionIn this study, the relationship between climatic factors and their effects on the hydrologicalconditions such as the river discharge, water level of Urmia Lake and wells water table werestudied. For presence or absence of relationship between them, the Pearson correlationcoefficient was used. The highest correlation between the water table and lake water level was0.71 which is significant at the level of 0.05. Among the four effective independent variables,the lowest correlation was observed between climate change and the water level of the lake. Thecoefficient for the river discharge and the water table was, respectively, 0.72 and -0.71. ThePearson correlation test shows that linear gradient during the period is significant with timeincreasing. The results indicate that the relationship between the precipitation and water level isnegative and temperature and the water table is positive. The regression gradient line at thescatter plot shows that the precipitation increase raises the water level. The highest annualdecreasing rainfall is -2.56. Increasing temperatures and declining rainfall, snowfall reduction,increasing evapotranspiration and reducing the water as input decreased the water level of thelake. As a result, the lake water level trend was decreasing 0.18 mm in each year. The modeland the regression analysis were calculated due to the delayed effects of climate andhydrological factors interference in each other. The coefficient determination indicates thatother factors remain constant; approximately 0.30 of the dispersion of the observed changes inthe lake water level is justified by temperature and precipitation variations. If we assume thathydrology parameters are constant, we can say that lake water level increases 0.005 meters perone mm rainfall and the lake water increases 1.672 meter per one cm river discharge.ConclusionBy designing a hydrology model, it was determined that 42 percent of water level fluctuations isdue to changes in the river discharge of the region and groundwater and water table. Byexamining regression models, we find that changes in hydrological parameters that are related tohuman factors rather than climatic parameters have the most influential effects on the lake waterlevel fluctuations. The temperature increase affected the lake water level dropping more than thePhysical Geography Research Quarterly, 46 (1), Spring 2014 15rainfall decrease. By examining Man-Kendall graphics, we characterized that leaping intemperature started in 1993. Precipitation and discharge decreasedin1993-1994 and this causedthe rise of the trend water table and reducing of water level in Urmia Lake, happened with afour-year delay which started from 1998.}, keywords = {discharge,precipitation,temperature,Urmia Lake,Water table}, title_fa = {تحلیل هیدروکلیماتولوژیکی نوسان‎های سطح آب دریاچۀ ارومیه}, abstract_fa = {دریاچۀ ارومیه از مهم‌ترین اکوسیستم‌های آبی ایران است که تغییر در آن، تأثیرات گسترده‌ای در وضعیت اقلیمی، اقتصادی ـ اجتماعی و هیدرولوژی خواهد گذاشت. برای بررسی ارتباط نوسان‌های سطح آب دریاچۀ ارومیه با تغییرات دما، بارش، سطح ایستابی و دبی رودخانه‌ها، سری‌های زمانی متغیرهای مذکور طی دورۀ آماری 2010- 1981جمع‌آوری و تنظیم شد. همگنی و تصادفی‎بودن داده‌ها به‎کمک آزمون ناپارامتریک ران تست مورد بررسی قرار گرفت. برای بررسی روند تغییرات متغیرها و میزان تأثیرگذاری متغیرهای مستقل بر متغیر وابسته (سطح آب دریاچۀ ارومیه)، از روش­های ناپارامتری من ـ کندال و پارامتری ضریب همبستگی پیرسون و تحلیل رگرسیون استفاده شد. نتایج نشان می‌دهد که کمابیش30 درصد از تغییرات سطح آب دریاچه با متغیرهای دما و بارش توجیه می‌شود. مدل‌های هیدرولوژی مشخص می‎کنند که 42 درصد از نوسانات سطح آب دریاچه، ناشی از تغییرات دبی رودخانه‌های منطقه و سطح ایستابی آبهای زیرزمینی است و افزایش دما بیشتر از کاهش بارندگی در افت سطح آب دریاچۀ ارومیه مؤثر است. این مطالعه نشان داد که جهش و روند افزایشی دما از سال 1993، کاهش بارش و دبی رودخانه‌ها از سال 1994، روند افزایشی ارتفاع سطح ایستابی و روند کاهشی سطح آب دریاچۀ ارومیه با تأخیر چهار ساله، از سال 1998 آغاز‌ شده است.}, keywords_fa = {بارش,دبی,دریاچۀ ارومیه,دما,سطح ایستابی}, url = {https://jphgr.ut.ac.ir/article_50620.html}, eprint = {https://jphgr.ut.ac.ir/article_50620_1788c806101c73fea2c26f0c6c0bad66.pdf} }