starting date demonstrated an earlier bloom initiation. Bloom behavior may be
realigning to pre-2006 dynamics (bloom starting date is influenced by winter crop
season productivity). Therefore, 2010–2011 could be identified as another turning
point for the environmental system, after the 2006–2007 event, connected to a drop
in accumulated temperature and hot season duration in 2011 compared to previous
years (2009 and 2008).
5 Conclusions
Remote sensing provides crucial information on inland water quality, as well as the
environmental factors that cause changes in water quality and ecosystem dynamics.
Algal bloom events are strongly connected to human activities within a watershed,
such as agriculture, demographic change, and economic development. Water quality and algal bloom management can no longer be limited to nutrient discharge
control, but needs to take into account indirect factors related to watershed management (e.g., agriculture and aquaculture), as well as local and regional short-term
climatic effects [30]. It is important that more complex scenarios are taken into
account, requiring an integrated approach to data acquisition and information
availability on finer spatial and temporal scales.
In this case study, we used an integrated watershed approach, based on remote
sensing, to gather information about the environmental dynamics of a complex lake
watershed (Lake Taihu), where algal blooms have caused a significant loss of
ecosystem services and other uses of water. Our integrated analysis identified two
distinct temporal patterns of algal bloom events, with an associated change in land
use and environmental conditions. Prior to 2006, algal bloom initiation date was
linked to land cover, in particular to winter crop productivity and the subsequent
nutrient loading into the lake. After 2007, there was an inversion in this relationship
between land cover and algal bloom dynamics, suggesting that nutrient saturation
had occurred and other environmental factors, such as temperature and winter crop
seasonality, became more important. After 2008, the situation seems to have
returned to pre-2006 conditions with less intense bloom events up to 2013.
Our results indicate not only that remote sensing can provide crucial information
for monitoring Lake Taihu watershed dynamics but also provides new insights into
an integrated approach to monitoring and managing inland water bodies. Future
research on the integrated assessment at a watershed scale could build on this
approach by including additional environmental features: hydrology (e.g., water
level, inflowing river regimes), meteorology (e.g., winds, precipitation time series),
and sediment biogeochemistry. Additional information would provide further
insights when placed within a comprehensive framework for watershed assessment.
Eventually, a sub-watershed scale of analysis of environmental features within the
watershed would help to identify localized phenomena.
Using Remote Sensing to Assess the Impact of Human Activities on Water. . .
107
realigning to pre-2006 dynamics (bloom starting date is influenced by winter crop
season productivity). Therefore, 2010–2011 could be identified as another turning
point for the environmental system, after the 2006–2007 event, connected to a drop
in accumulated temperature and hot season duration in 2011 compared to previous
years (2009 and 2008).
5 Conclusions
Remote sensing provides crucial information on inland water quality, as well as the
environmental factors that cause changes in water quality and ecosystem dynamics.
Algal bloom events are strongly connected to human activities within a watershed,
such as agriculture, demographic change, and economic development. Water quality and algal bloom management can no longer be limited to nutrient discharge
control, but needs to take into account indirect factors related to watershed management (e.g., agriculture and aquaculture), as well as local and regional short-term
climatic effects [30]. It is important that more complex scenarios are taken into
account, requiring an integrated approach to data acquisition and information
availability on finer spatial and temporal scales.
In this case study, we used an integrated watershed approach, based on remote
sensing, to gather information about the environmental dynamics of a complex lake
watershed (Lake Taihu), where algal blooms have caused a significant loss of
ecosystem services and other uses of water. Our integrated analysis identified two
distinct temporal patterns of algal bloom events, with an associated change in land
use and environmental conditions. Prior to 2006, algal bloom initiation date was
linked to land cover, in particular to winter crop productivity and the subsequent
nutrient loading into the lake. After 2007, there was an inversion in this relationship
between land cover and algal bloom dynamics, suggesting that nutrient saturation
had occurred and other environmental factors, such as temperature and winter crop
seasonality, became more important. After 2008, the situation seems to have
returned to pre-2006 conditions with less intense bloom events up to 2013.
Our results indicate not only that remote sensing can provide crucial information
for monitoring Lake Taihu watershed dynamics but also provides new insights into
an integrated approach to monitoring and managing inland water bodies. Future
research on the integrated assessment at a watershed scale could build on this
approach by including additional environmental features: hydrology (e.g., water
level, inflowing river regimes), meteorology (e.g., winds, precipitation time series),
and sediment biogeochemistry. Additional information would provide further
insights when placed within a comprehensive framework for watershed assessment.
Eventually, a sub-watershed scale of analysis of environmental features within the
watershed would help to identify localized phenomena.
Using Remote Sensing to Assess the Impact of Human Activities on Water. . .
107