Temporal and spatial changes of water quality and management strategies of Dianchi Lake in southwest China

Abstract

Abstract. Temporal and spatial changes to the water quality of Dianchi Lake in southwest China were investigated using monthly monitoring data from 2005 to 2012. Dianchi Lake is divided into two parts, Caohai Lake and Waihai Lake, by a man-made dike. Caohai Lake lies at the north of Dianchi Lake, while Waihai Lake is the main water body of Dianchi Lake and accounts for 96.7 % of the whole area of the lake. Based on the analysis of total phosphorus (TP), total nitrogen (TN), and chlorophyll a (Chl a) concentrations, it was determined that, in Caohai Lake, the annual concentrations of these variables ranged from 0.19-1.46 mg L −1 , 6.11-16.79 mg L −1 , 0.06-0.14 mg L −1 , respectively. In addition, the annual concentrations of TP, TN and Chl a in Waihai Lake ranged between 0.13 and 0.20 mg L −1 , 1.82 and 3.01 mg L −1 , and 0.04 and 0.09 mg L −1 , respectively. Cluster analysis (CA) classified the 10 monitoring sites into two clusters (cluster A and cluster B) based on similarities of water quality characteristics. Our data revealed that the current status of water quality within Caohai Lake was much worse than that of Waihai Lake. Water quality was seriously degraded during the economic boom near the period of the "Eleventh Five-Year Plan" (2005)(2006)(2007)(2008)(2009)(2010), and gradually improved from 2010 to 2012 because of the "standard emission directive to industry". The main factors that influenced the spatial and temporal changes to water quality were natural factors including lake evolution and regional characteristic as well as human factors such as pollution load into the lake and management strategies that were already adopted. Some activities and regulations were implemented to enhance the lake environment by controlling wastewater emissions and establishing regulations to protect the lakes in the Yunnan Province. However, problems with institutional fragmentation (horizontal and vertical), simple treatment methods, low-intensity investment in pollution control, and lack of meaningful endogenous pollution control strategies were still present in the lake management strategy. To solve these problems, suitable control measures are needed, especially considering the current old-age status of Dianchi Lake. The fundamental improvement of the water quality within Caohai Lake was dependent on the measures taken in the upper reaches of the Caohai Watershed, including further recovery of submerged plants, resource utilization by floating plants and the reinforcement of sediment disposal. Management strategies for endogenous pollution in Waihai Lake were mainly dependent on restocking algae-eating fish and the ecological restoration of macrophytes. In this way, the swamping trend and the ageing process that is occurring in Dianchi Lake can be stunted. And the management strategies would be a contribution to the management of water conflicts between mankind and ecosystems in similar lakes.

Characteristics of bioavailable organic phosphorus in sediment and its contribution to lake eutrophication in China

“…Principal initiatives have included the control of inflowing river pollution and lake peripheral pollution interception as well as in-lake ecological dredging and restoration (Liu et al, 2014). The external input of P has fallen to historic lows because of the implementation of the stringent "Zero O'clock Action" policy (Zhang et al, 2014;Zhu, 2008). However, the eutrophication statuses of the two lakes are not fundamentally solved but continue to worsen.…”

Effect of Phragmites japonicus harvest frequency and timing on dry matter yield and nutritive value

“…According to monitoring data from 2005 to 2012, the annual concentrations of total N ranged from 1.82 to 3.01 mg L À1 , and those of total P ranged from 0.13 to 0.20 mg L À1 in the main water body of Lake Dianchi (Zhang et al, 2013). To mitigate the eutrophication of the lake, a large number of CWs were established along the lakeside.…”

Temporal Variation and Reduction Strategy of Nutrient Loads from an Urban River Catchment into a Eutrophic Lake, China

“…Caohai Lake comprises a total area of about 10.7 km 2 and suffers from eutrophication as a result of excessive nutrient input from Kunming City [29]. Seven urban rivers contribute the majority of nutrient loads into Caohai Lake, which is more eutrophic than the southern section of Dianchi Lake [30]. To facilitate the recovery of Dianchi Lake from eutrophication, the project of Niulanjiang River-Dianchi Lake Water Replenishment diverts an annual average volume of 6.0 × 10 8 m 3 fresh water to Dianchi Lake since 2014, which half of the water is diverted to Caohai Lake through Daguanhe River [31,32].…”