12 Sediment Management in River Basins: An Essential Element …
277
12.4.1 Measurements of Suspended Load Concentration
The main part of the research is based on measurements of suspended load concentration in the longitudinal profile of the Vistula waters at the navigable reach of the
river (on the distance more than 900 km). Research on total suspension was carried
out in relation to two spatial aspects:
– heterogeneity of load in single cross-sectional profiles—to identify bottom and
lateral erosion zones,
– heterogeneity of load on the longitudinal profile—to define the influence range
of erosion processes/accumulation zones. We used mobile turbidimeter HACH
2100QIS (in FNU) and LISST 25X sensor (Laser In Situ Scattering Transmissometer manufactured by Sequoia Scientific Inc.) for suspended load measurement devices able to measure concentration in mg·l
−1 and to differentiate specific
grain size fractions. The instrument measures particles in two classes. In the range
of 2.5–63 micron, and the other in the range of 63–500 micron. Turbidimeters are
easy to use and most popular devices for suspended sediments monitoring [93].
From the research carried out in May 2018, in the longitudinal profile of the
Vistula, several characteristic fragments can be distinguished, with a different course
of the water turbidity. The recorded values reflect the sources of supply and the
extent of the basin’s transformation. The first section (0–92 km) is characterized
by the presence of a cascade of retention reservoirs (Dwory, Smolice, Ł˛ aczany,
Ko´ sciuszko, D˛ abie, and Przewóz), which affects the large variation of water turbidity
(10–60 FNU, average 20 FNU). Then (up to approx. 420 km of the river’s course)
there is a systematic increase in water turbidity as a result of the supply of suspended
sediment from the Carpathian tributaries, reaching a level of about 40 FNU. Between
the estuary of the Wieprz and Pilica Rivers, there is a zone of increased accumulation
of suspended load, which is marked by a clear decrease in water turbidity to about
30 FNU (Fig. 12.4). Below Warsaw, the influence of transformations of the Vistula
river bed and local sources of sediment supply is noted. At km 551, the turbidity of
the Vistula is once again drastically reduced (to about 20 FNU) as a result of the
Narew River water supply—with slight turbidity (accumulation in the Zegrzy´ nski
Reservoir). Up to 624 km of the Vistula River (Płock), there is a systematic increase in
the turbidity of waters because of the impact of the backwater zone of the Włocławek
Reservoir. The turbidity of water in the reservoir (up to 672 km) drops even to the level
below 10 FNU (Fig. 12.4), which reflects the accumulation role of hydrotechnical
constructions in suspended sediment transport. Below the water dam of Włocławek,
up to the estuary, the turbidity of waters undergoes systematic, though slight increase
(up to about 15 FNU), which indicates the renewal of suspended sediment.
Investigations of the particle size distribution of suspended sediments in the longitudinal profile of the Vistula River may enable diversification of its supply sources,
and in the cross profile determine the impact of hydrological and morphometric conditions on the dynamics of its transport. At selected sites in the longitudinal profile of
the Vistula: Płock, Bydgoszcz, Kiezmark (Fig. 12.5) research was conducted at two
277
12.4.1 Measurements of Suspended Load Concentration
The main part of the research is based on measurements of suspended load concentration in the longitudinal profile of the Vistula waters at the navigable reach of the
river (on the distance more than 900 km). Research on total suspension was carried
out in relation to two spatial aspects:
– heterogeneity of load in single cross-sectional profiles—to identify bottom and
lateral erosion zones,
– heterogeneity of load on the longitudinal profile—to define the influence range
of erosion processes/accumulation zones. We used mobile turbidimeter HACH
2100QIS (in FNU) and LISST 25X sensor (Laser In Situ Scattering Transmissometer manufactured by Sequoia Scientific Inc.) for suspended load measurement devices able to measure concentration in mg·l
−1 and to differentiate specific
grain size fractions. The instrument measures particles in two classes. In the range
of 2.5–63 micron, and the other in the range of 63–500 micron. Turbidimeters are
easy to use and most popular devices for suspended sediments monitoring [93].
From the research carried out in May 2018, in the longitudinal profile of the
Vistula, several characteristic fragments can be distinguished, with a different course
of the water turbidity. The recorded values reflect the sources of supply and the
extent of the basin’s transformation. The first section (0–92 km) is characterized
by the presence of a cascade of retention reservoirs (Dwory, Smolice, Ł˛ aczany,
Ko´ sciuszko, D˛ abie, and Przewóz), which affects the large variation of water turbidity
(10–60 FNU, average 20 FNU). Then (up to approx. 420 km of the river’s course)
there is a systematic increase in water turbidity as a result of the supply of suspended
sediment from the Carpathian tributaries, reaching a level of about 40 FNU. Between
the estuary of the Wieprz and Pilica Rivers, there is a zone of increased accumulation
of suspended load, which is marked by a clear decrease in water turbidity to about
30 FNU (Fig. 12.4). Below Warsaw, the influence of transformations of the Vistula
river bed and local sources of sediment supply is noted. At km 551, the turbidity of
the Vistula is once again drastically reduced (to about 20 FNU) as a result of the
Narew River water supply—with slight turbidity (accumulation in the Zegrzy´ nski
Reservoir). Up to 624 km of the Vistula River (Płock), there is a systematic increase in
the turbidity of waters because of the impact of the backwater zone of the Włocławek
Reservoir. The turbidity of water in the reservoir (up to 672 km) drops even to the level
below 10 FNU (Fig. 12.4), which reflects the accumulation role of hydrotechnical
constructions in suspended sediment transport. Below the water dam of Włocławek,
up to the estuary, the turbidity of waters undergoes systematic, though slight increase
(up to about 15 FNU), which indicates the renewal of suspended sediment.
Investigations of the particle size distribution of suspended sediments in the longitudinal profile of the Vistula River may enable diversification of its supply sources,
and in the cross profile determine the impact of hydrological and morphometric conditions on the dynamics of its transport. At selected sites in the longitudinal profile of
the Vistula: Płock, Bydgoszcz, Kiezmark (Fig. 12.5) research was conducted at two