Evaluation of the effects of climate change on meteorological and hydrological parameters using climatic models and Mann – Kendall test (case study: Urmia Lake)

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J. Bio. & Env. Sci. 2014 Where xi is <strong>the</strong> concerned variable and x is <strong>the</strong> mean <strong>of</strong> concerned variable. If t t , n 2 , regression gradient is considered 2 insignificant (hypo<strong>the</strong>sis <strong>of</strong> H0 equal with gradient b is zero and if gradient b is significantly different with zero, it is represents <strong>the</strong> existence <strong>of</strong> trend). Results and Discussion In this research, <strong>the</strong> amounts <strong>of</strong> precipitation and temperature was predicted in order to investigate <strong>the</strong> <strong>effects</strong> <strong>of</strong> <strong>climate</strong> <strong>change</strong> on hydrological parameters <strong>of</strong> Urmia Lake watershed and also, trend <strong>of</strong> water level variations from precipitation, maximum and minimum temperature, relative humidity, sunshine hours data using downscaling <strong>of</strong> GCM and HADCM3 models. Also, monthly discharge data in hydrometric index stations and mean monthly temperature, precipitation and evaporation were used to train, validating and testing <strong>the</strong> model. Variations trend <strong>of</strong> <strong>the</strong> lake water level was investigated using Mann- Kendall which its results have been explained in continue. Table 1. Synoptic stations position. X 14 /80 13 /80 Mann-Kendall Y 80 /80 83 /38 stations Tabriz Urmia In this study, <strong>the</strong> data from base studies <strong>of</strong> meteorological and hydrological reports <strong>of</strong> integrated management <strong>of</strong> water resources <strong>of</strong> Urmia Lake watershed have been investigated. The studied data should be homogenous statistically. Investigation <strong>of</strong> data homogeneity was done using double mass curve. After data preparation <strong>the</strong> trend <strong>of</strong> meteorological and hydrological factors affecting Urmia Lake watershed was investigated. In this regard, <strong>the</strong> variations trend <strong>of</strong> temperature, precipitation, evaporation in <strong>the</strong> lake surface, surface run<strong>of</strong>f entering <strong>the</strong> lake, variations <strong>of</strong> <strong>the</strong> Lake water level and volume parameters were investigated using Mann-Kendall test and linear regression. The results <strong>of</strong> Mann-Kendall and regression method have been reported in Tables (3) and (4). Mean precipitation volume on <strong>the</strong> lake and evaporation from <strong>the</strong> lake surface have had a significant reduction. Also, results <strong>of</strong> Mann-Kendall test show an ascending trend for temperature parameter. According to <strong>the</strong> results <strong>of</strong> linear regression test, descending trend <strong>of</strong> mean inflow to Urmia watershed and evaporation has an important trend. Also, <strong>the</strong> results <strong>of</strong> this test, reveals <strong>the</strong> importance <strong>of</strong> temperature ascending trend. Evaporation from <strong>the</strong> lake surface has experienced a temperature descending trend during <strong>the</strong> recent years with regard to ascending trend <strong>of</strong> temperature which can be due to reduction <strong>of</strong> Urmia Lake area and increase <strong>of</strong> <strong>the</strong> lake water salinity. Generally, <strong>the</strong> results <strong>of</strong> this research suggest that, mean precipitation in Urmia is between 300 and 350 mm and mean temperature was 11 to 15 ⁰C so; <strong>the</strong> amount <strong>of</strong> temperature was not as much to be attributed entirely for <strong>the</strong> lake water level variations. These results are also predictable for o<strong>the</strong>r watersheds in Iran and should be considered. Table 2. Hydrometric stations position. H 4488 4188 4838 4188 4388 4383 4888 4808 Temperature X 14 /83 14 /1 14 /43 13 /3 13 /88 11 /03 13 /83 13 /48 Y 83 /13 84 /84 84 /43 84 /40 83 83 /18 83 /80 84 /3 Stations Tazekand Polanian Dashband Beytas Peyghale Mirabad Dizag Kuter Table (5) shows <strong>the</strong> results <strong>of</strong> Mann-Kendall test for monthly minimum and maximum temperature in index synoptic stations. The results show that, temperature has an ascending trend or no trend in Tabriz station while, Urmia has a descending trend or no trend. Mean amount <strong>of</strong> 117 | Khaneshan et al
J. Bio. & Env. Sci. 2014 temperature in <strong>the</strong> observation period (1961-2001) and its mean value in <strong>the</strong> prediction period (2010- 2100) have been shown in Table (3), (4) and (6). The difference between <strong>the</strong>se values represents temperature variations in <strong>the</strong> future. Precipitation Table (7) presents <strong>the</strong> results <strong>of</strong> Mann-Kendall test for monthly and annual mean precipitation in two index synoptic stations. The results show that, <strong>the</strong> stations have descending trend or no trend. Mean values <strong>of</strong> precipitation in observations and predictions period have been presented in Fig.5 and Table (8). Table 3. Results <strong>of</strong> Mann-Kendall (for confidence level <strong>of</strong> 95%). Time series Autocorrelation Zs Possibility <strong>of</strong> significant trend coefficient existence level Mean water level <strong>of</strong> <strong>the</strong> lake 0.82 -0.17 Yes Mean precipitation height on <strong>the</strong> lake 0.3 -0.22 No Mean surface inflow 0.17 -2.2 Yes Mean precipitation volume on <strong>the</strong> lake 0.3 -1.9 Yes Mean evaporation height from <strong>the</strong> pan 0.48 -3.4 Yes Mean evaporation height from <strong>the</strong> lake 0.68 -2.7 Yes Lake volume variations 0.74 -0.6 No Temperature variations 0.43 2.6 Yes Table 4. Results <strong>of</strong> linear regression test. Time series Regression equation Gradient in confidence P value R2 range <strong>of</strong> 90% Mean water level <strong>of</strong> <strong>the</strong> lake Y= -8/ 8X + 4830 - 8/8 ،8/88 8 /838 0 /1% Mean precipitation height on <strong>the</strong> lake low Mean surface inflow Y= -8/ 43X + 838 - 8/43 ،4/88 8 /08 8 /84% Mean precipitation volume on <strong>the</strong> lake low Mean evaporation height from <strong>the</strong> pan Y= -03/ 8X + 48880 - 03/8 ،28/8 8 /880 48 /1% Mean evaporation height from <strong>the</strong> lake high Lake volume variations Y= -1/ 38X + 4110 - 1/38 ،0/2 8 /80 8 /4% low Mean water level <strong>of</strong> <strong>the</strong> lake Y= -3/ 8X + 4238 - 3/8 ،8/2 - 3 E 8 /81 88 /4% Mean precipitation height on <strong>the</strong> lake high Mean surface inflow Y= -88/ 0X + 3313 - 88/0 ،43/8 8 /884 81 /8% Mean precipitation volume on <strong>the</strong> lake high Mean evaporation height from <strong>the</strong> pan Y= -48/ 84X + 48481 - 48/84 ،48481 8 /30 8 /8% Mean evaporation height from <strong>the</strong> lake low Lake volume variations Y= -8/ 81X + 0/82 - 8/81 ،8/88 8 /881 48 /8% high Evaporation Table (9) show <strong>the</strong> results <strong>of</strong> Mann-Kendall test for monthly evaporation in index synoptic stations. The results show that, <strong>the</strong> stations have an ascending trend in <strong>the</strong> amount <strong>of</strong> evaporation. Mean values <strong>of</strong> evaporation in observation and prediction period have been shown in Fig.6 and Table (10). 118 | Khaneshan et al
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Evaluation of the effects of climate change on meteorological and hydrological parameters using climatic models and Mann – Kendall test (case study: Urmia Lake)

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