Effects of water level and climate on the hydrodynamics and water quality of Anvil Lake, Wisconsin, a shallow seepage lake

Robertson DM, Juckem PF, Dantoin ED, Winslow LA. 2018. Effects of water level and climate on the hydrodynamics and water quality of Anvil Lake, Wisconsin, a shallow seepage lake. Lake Reserv Manage. 34:00–00. Interannual differences in the water quality of Anvil Lake, Wisconsin, were examined to determine how water level and climate affect the hydrodynamics and trophic state of shallow lakes, and their importance compared to anthropogenic changes in the watershed. Anvil Lake is a relatively pristine seepage lake with hydrology dominated by precipitation, evaporation, and groundwater exchange enabling the typically subtle effects of water level and climate to be evaluated. Groundwater and hydrodynamic models were used to describe lake water and phosphorus budgets and how its hydrodynamics are affected by water level and air temperature. Decreases in water level are expected to cause Anvil Lake and other shallow lakes to stratify fewer days, and have warmer bottom temperatures and more deep-mixing events. Increasing air temperatures should cause these lakes to have shorter ice cover, longer summer stratification periods, and warmer bottom temperatures. How water level affects water quality depends on how nutrient loading and lake volume vary: during drier, low-water years, lakes with large interannual changes in loading should have better water quality, whereas lakes with small changes in loading should degrade slightly. Anthropogenic changes in Anvil Lake's watershed over the past ∼100 yr were about 1.5 times the effects of changes in water level when levels were low, but the effects were similar when levels were high. Climate warming is expected to increase productivity in shallow lakes because warmer air temperatures will likely increase bottom temperatures increasing sediment phosphorus release and deep-mixing events enabling this phosphorus to reach the epilimnion.

Robertson DM、Juckem PF、Dantoin ED、Winslow LA 于2018年发表了题为《威斯康星州安维尔湖水位与气候对水动力及水质的影响——一座浅渗滤湖》的研究，刊载于《Lake Reserv Manage（湖泊与水库管理）》期刊，卷34，页码00–00。本研究以威斯康星州安维尔湖的水质年际差异为研究对象，旨在明确水位与气候如何影响浅湖的水动力过程与营养状态，并对比其与流域人为活动变化的相对重要性。安维尔湖属于相对原生的渗滤型湖泊，水文过程以降水、蒸发及地下水交换为主导，这使得水位与气候的细微影响效应得以精准评估。研究采用地下水与水动力模型，刻画了湖体水与磷素的收支特征，以及水位与气温对湖体水动力过程的影响机制。研究预测，水位下降将使安维尔湖及其他浅湖的热力分层天数减少，底层水温升高，且深层混合事件更为频发。气温升高则会导致这类湖泊的冰盖期缩短、夏季热力分层持续时间延长，同时底层水温进一步升高。水位对湖泊水质的影响取决于营养盐负荷与湖体容积的变化规律：在干旱低水位年份，营养盐负荷年际波动幅度较大的湖泊水质将有所改善，而负荷波动较小的湖泊水质则会出现小幅退化。过去约100年间，安维尔湖流域的人为活动变化强度在低水位时期约为水位变化影响的1.5倍，但在高水位时期两者的影响程度基本相当。气候变暖预计将提升浅湖的初级生产力：由于气温升高会抬升底层水温，促进沉积物磷素释放，同时增加深层混合事件，使这些磷素能够抵达湖上层（epilimnion）。