2.5 Landscape Impact on Water Characteristics
Generally, tropical areas are distinguished by having substantial seasonality in
climate with distinct dry and wet seasons (Ferreira et al. 2017). Furthermore, in
humid tropics, hydrological processes have higher energy inputs and are subjected to
quick changes, basically related to human intervention (Wohl et al. 2012). Surface
runoff that affects water quality is itself affected by climate and land uses in the area
(Singh et al. 2004). Several researchers have reported that forest and grass areas
normally have a positive impact on water quality (Lee et al. 2009; Walker et al.
2009), while residential and agricultural areas have a negative influence on the
quality of water (Bu et al. 2014; Namugize Jean et al. 2018). Shehab et al. (2020)
have also found that forest cover is normally related to good water quality and plays
a considerable role in enhancing water quality in different watersheds worldwide
(Oliveira et al. 2016). Forest areas are found to be negatively related to numerous
water quality characteristics in each season. This result reinforces the idea that forest
and grass areas have a fixation and absorption impact on pollutants in river systems
(Bu et al. 2018). In addition, forest cover functions as a filter or a sieve that screens
and reduces the contaminants and sediments conveyed with the runoff (Ding et al.
2013). Furthermore, grass acts as a retaining agent that lessens the amount of surface
runoff (Ouyang et al. 2010).
Several studies have illustrated that mostly, urban and agricultural lands have
adverse effects on water quality (Ou et al. 2016; Huang et al. 2016). Excessive use of
fertilizers and soil erosion can result in higher deposition of nutrients, organic matter,
and sediments in water (Poudel 2016). Additionally, the level of negative impact of
agricultural lands on water quality is highly influenced by the geographic location as
well as farming techniques and habits (Jeon et al. 2004). Comparably, the surge in
wastewater discharge and effluent from residential areas as well as contaminants
buildup on impervious tops leads to decline in water quality (Ding et al. 2016). It is a
well-known fact that residential areas contribute primarily to water quality degradation (White and Greer 2006), even with relatively small percentage of urban domain,
the effects that it exerts on water quality are exceptionally strong and significant
(Zhou et al. 2012). Residential areas are found to be positively related to most
variables in both seasons (Shehab et al. 2020).
In addition to the spatial effect on water quality, there is an obvious temporal
impact related to seasonal changes. Huang et al. (2016) stated that seasonal variations in hydrological processes like precipitation, runoff, interception, and abstraction have a major influence on the river flow, which lead to different levels of
sediments and nutrients from one season to another. However, Woli et al. (2004)
mentioned that during the normal season, agricultural applications should not be
used to determine the nutrients variability in spite of the fertilizer usage. Therefore,
river quality deterioration would have to be attributed to other sources. In this case,
the residential and industrial areas, which are also heavily correlated with most water
quality parameters in the normal season, become the main suspect. The sewerage
points that are normally scattered in the populated areas as well as the industrial
30
N. R. Jamil and Z. N. Shehab
Generally, tropical areas are distinguished by having substantial seasonality in
climate with distinct dry and wet seasons (Ferreira et al. 2017). Furthermore, in
humid tropics, hydrological processes have higher energy inputs and are subjected to
quick changes, basically related to human intervention (Wohl et al. 2012). Surface
runoff that affects water quality is itself affected by climate and land uses in the area
(Singh et al. 2004). Several researchers have reported that forest and grass areas
normally have a positive impact on water quality (Lee et al. 2009; Walker et al.
2009), while residential and agricultural areas have a negative influence on the
quality of water (Bu et al. 2014; Namugize Jean et al. 2018). Shehab et al. (2020)
have also found that forest cover is normally related to good water quality and plays
a considerable role in enhancing water quality in different watersheds worldwide
(Oliveira et al. 2016). Forest areas are found to be negatively related to numerous
water quality characteristics in each season. This result reinforces the idea that forest
and grass areas have a fixation and absorption impact on pollutants in river systems
(Bu et al. 2018). In addition, forest cover functions as a filter or a sieve that screens
and reduces the contaminants and sediments conveyed with the runoff (Ding et al.
2013). Furthermore, grass acts as a retaining agent that lessens the amount of surface
runoff (Ouyang et al. 2010).
Several studies have illustrated that mostly, urban and agricultural lands have
adverse effects on water quality (Ou et al. 2016; Huang et al. 2016). Excessive use of
fertilizers and soil erosion can result in higher deposition of nutrients, organic matter,
and sediments in water (Poudel 2016). Additionally, the level of negative impact of
agricultural lands on water quality is highly influenced by the geographic location as
well as farming techniques and habits (Jeon et al. 2004). Comparably, the surge in
wastewater discharge and effluent from residential areas as well as contaminants
buildup on impervious tops leads to decline in water quality (Ding et al. 2016). It is a
well-known fact that residential areas contribute primarily to water quality degradation (White and Greer 2006), even with relatively small percentage of urban domain,
the effects that it exerts on water quality are exceptionally strong and significant
(Zhou et al. 2012). Residential areas are found to be positively related to most
variables in both seasons (Shehab et al. 2020).
In addition to the spatial effect on water quality, there is an obvious temporal
impact related to seasonal changes. Huang et al. (2016) stated that seasonal variations in hydrological processes like precipitation, runoff, interception, and abstraction have a major influence on the river flow, which lead to different levels of
sediments and nutrients from one season to another. However, Woli et al. (2004)
mentioned that during the normal season, agricultural applications should not be
used to determine the nutrients variability in spite of the fertilizer usage. Therefore,
river quality deterioration would have to be attributed to other sources. In this case,
the residential and industrial areas, which are also heavily correlated with most water
quality parameters in the normal season, become the main suspect. The sewerage
points that are normally scattered in the populated areas as well as the industrial
30
N. R. Jamil and Z. N. Shehab