3.4.2 Monthly changes
Similar to the annual variation (Fig. S5), the monthly mean TLI( Σ ) values of both Shahe Reservoir and Chengxi Reservoir varied over a wide range (41.80 ~ 48.85 and 39.20 ~ 45.35), whereas those of Huanglishu Reservoir varied over a smaller range (43.43 ~ 47.35). The maximum monthly mean TLI( Σ ) values generally occurred from August to October, the minimum TLI( Σ ) values generally occurred from April to June, as well as all three reservoirs showed a very clear upward trend from June to August (summer months), probably due to the effect of temperature on algae. This phenomenon indirectly confirms that temperature is one of the causes that influence changes in the eutrophication of water bodies (Herb and Stefan, 2003). Besides, through the comparison, it was found that the TLI( Σ ) value of Chengxi Reservoir was lower than that of Huanglishu Reservoir and Shahe Reservoir in all the months, and it can also be concluded that the water quality of Chengxi Reservoir is better than that of Huanglishu Reservoir and Shahe Reservoir.