Developing water quality maps of a hyper-saline lake using spatial interpolation methods

Urmia Lake, the second largest hyper-saline lake in the world, has experienced a significant drop in water level during the last decade. This study was designed to examine the water quality of Urmia Lake and to characterize the spatial heterogeneity and temporal changes of the physico-chemical parameters between October 2009 and July 2010. Two spatial interpolation methods, Inverse Distance Weighting (IDW) and Ordinary Kriging (OK), were used and compared with each other to derive the spatial distribution of ionic constituents as well as TDS and density along the lake. Results showed that the main dominant cations and anions in Urmia Lake were Na+, Mg++, K+, Ca++, Cl- , SO4--, and HCO3-, respectively. Although water quality of the lake is homogeneous with depth, it differs between the northern and southern parts. Water quality also varies seasonally, determined by river inflows and the lake bathymetry. Moreover, with the present salinity level, salt precipitation is likely in Urmia Lake and is becoming one of the principal factors determining the distribution of solutes within the lake. This study shows that the combined use of temporal and spatial water quality data improves our understanding of complex, large aquatic systems like Urmia Lake.

乌尔米亚湖，作为世界上第二大的超咸水湖，在过去十年中经历了显著的水位下降。本研究旨在审视乌尔米亚湖的水质状况，并描述该湖在2009年10月至2010年7月期间物理化学参数的空间异质性和时间变化。采用了两种空间插值方法，即反距离权重法（Inverse Distance Weighting, IDW）和普通克里金法（Ordinary Kriging, OK），并将它们相互比较，以推导出湖中离子成分、总溶解固体（TDS）以及密度沿湖的分布。研究结果揭示了乌尔米亚湖中主要的优势阳离子和阴离子分别为Na+、Mg2+、K+、Ca2+、Cl-、SO42-和HCO3-。尽管湖水的质量在深度上保持均一，但南北部分之间存在差异。水质亦随季节变化，受河流入流和湖泊地形的影响。此外，鉴于当前盐度水平，乌尔米亚湖中可能出现盐析现象，并正成为决定湖内溶质分布的主要因素之一。本研究表明，结合时间和空间水质数据能够增进我们对像乌尔米亚湖这样复杂的大型水生系统的理解。