Abstract
Abstract. Lake Urmia, a salt lake in the north-west of Iran, plays a valuable role in the environment, wildlife and economy of Iran and the region, but now faces great challenges for survival. The Lake is in immediate and great danger and is rapidly going to become barren desert. As a result, the increasing demands upon groundwater resources due to expanding metropolitan and agricultural areas are a serious challenge in the surrounding regions of Lake Urmia. The continuous GPS measurements around the lake illustrate significant subsidence rate between 2005 and 2009. The objective of this study was to detect and specify the non-linear correlation of land subsidence and temperature activities in the region from 2005 to 2009. For this purpose, the cross wavelet transform (XWT) was carried out between the two types of time series, namely vertical components of GPS measurements and daily temperature time series. The significant common patterns are illustrated in the high period bands from 180–218 days band (~6–7 months) from September 2007 to February 2009. Consequently, the satellite altimetry data confirmed that the maximum rate of linear trend of water variation in the lake from 2005 to 2009, is associated with time interval from September 2007 to February 2009. This event was detected by XWT as a critical interval to be holding the strong correlation between the land subsidence phenomena and surface temperature. Eventually the analysis can be used for modeling and prediction purposes and probably stave off the damage from subsidence phenomena.
Highlights
The subsidence of the Earth’s surface is a phenomenon that occurs in some places in the world, which overuses underground sources of water
This event was detected by XWT as a critical interval to be holding the strong correlation between the land subsidence phenomena and surface temperature
In order to study the temporal behavior of the deformation in high spatial resolution, Sedighi et al (2009) used InSAR observations consisting of four images acquired by ENVISAT satellite chosen from descending track 92 and ascending track 228 passes from 22 September 2003 to 24 May 2004
Summary
The subsidence of the Earth’s surface is a phenomenon that occurs in some places in the world, which overuses underground sources of water. Iran has a semi-arid and arid climate and the rate of rainfall is lower than the mean rate in the world It is faced with over-exploitation of groundwater in agricultural areas and extension of the cities and industrial areas. Due to recent years of progressive dry climate, the water level of Lake Urmia, has been dramatically dropped about 6 m during the last 20 yr (Jalili et al, 2011) This lake, as a closed lake, is located in an area where evaporation is greater than rainfall. Mogohgthatsaesde-dA-Azazrareettaal.l:.:LLaanndd ssuubbssiiddeenncceeiinnLLaakkeeUUrmrmiaia and domestic uses are the most important factors for water surface slump of this lake (Hassanzadeh et al, 2012) These types of lakes are sensitive to temperature changes. Extensive studies in geophysics and geodesy indicate the abilities of XWT and WTC in demonstration of relationships between time-frequency space of pairs of nonstationary time series (e.g. Torrence and Compo, 1998; Jevrejeva et al, 2003; Vedanti and Dimri, 2003; Grinsted et al, 2004; Kirby and Swain, 2004; Liu et al, 2005; Chamoli et al, 2006; Jevrejeva et al, 2006; Cazelles et al, 2007; Donner and Thiel, 2007; Liu et al, 2007; Valdes-Galicia and Velasco, 2007; Barbero and Moron, 2011)
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