Trend Analyses of Meteorological Variables and Lake Levels for Two Shallow Lakes in Central Turkey

Abstract

Trend analyses of meteorological variables play an important role in assessing the long-term changes in water levels for sustainable management of shallow lakes that are extremely vulnerable to climatic variations. Lake Mogan and Lake Eymir are shallow lakes offering aesthetic, recreational, and ecological resources. Trend analyses of monthly water levels and meteorological variables affecting lake levels were done by the Mann-Kendall (MK), Modified Mann-Kendall (MMK), Sen Trend (ST), and Linear trend (LT) methods. Trend analyses of monthly lake levels for both lakes revealed an increasing trend with the Mann-Kendall, Linear, and Sen Trend tests. The Modified Mann-Kendall test results were statistically significant with an increasing trend for Eymir lake levels, but they were insignificant for Mogan lake due to the presence of autocorrelation. While trend analyses of meteorological variables by Sen Test were significant at all tested variables and confidence levels, Mann-Kendall, Modified Mann-Kendall, and Linear trend provided significant trends for only humidity and wind speed. The trend analyses of Sen Test gave increasing trends for temperature, wind speed, cloud cover, and precipitation; and decreasing trends for humidity, sunshine duration, and pan evaporation. These results show that increasing precipitation and decreasing pan evaporation resulted in increasing lake levels. The results further demonstrated an inverse relationship between the trends of air temperature and pan evaporation, pointing to an apparent “Evaporation Paradox”, also observed in other locations. However, the increased cloud cover happens to offset the effects of increased temperature and decreased humidity on pan evaporation. Thus, all relevant factors affecting pan evaporation should be considered to explain seemingly paradoxical observations.

Quantifying the Relative Contribution of Climate Change and Anthropogenic Activities on Runoff Variations in the Central Part of Tajikistan in Central Asia

“…The application of the trend test to analyze the impact of climate change on runoff is a common practice implemented by many researchers [89][90][91]. In this study, the result of the modified MK test indicated that the trend of annual temperature and annual potential evapotranspiration significantly increased, while precipitation showed an insignificant decreasing trend in the upstream and downstream regions of the KRB.…”

Debi-Sürek Eğrisi Yardımıyla Taban Akımının Hesaplaması: Samsun Kürtün Irmağı Örneği

“…Ardından, xi veri sütunu başlangıç olarak kullanılır ve diğer sıralanmış xj ile Denklem 2'deki signum fonksiyonu kullanılarak Denklem 3'teki "S" değeri hesaplanır. Bu işlemler sonucunda tüm veri çiftlerinin farkı (xj−xi) ile pozitif ve negatif değerlerin sayısının toplamı bulunmuş olur (Demir & Keskin, 2020;Yagbasan, Demir, & Yazicigil, 2020).…”

Trend Analysis of Ground-Water Levels and The Effect of Effective Soil Stress Change: The Case Study of Konya Closed Basin

“…If (tcal) account value exceeds the accepted range, there is a trend and it is increasing or decreasing according to the sign. If it does not exceed (-tcritical <tcal <tcritical), it is said that there is no trend (V. Demir, 2018;Yagbasan et al, 2020).…”