Ideally,
existing water-level recording
sites in the Tisa River Basin are selected for renovation. However, when
necessary, new sites that require construction of a gage
house
are selected. Both the renovated sites and the new gage houses must be designed
to house equipment that measures and transmits water-level,
air-temperature, water-temperature, and precipitation data.
The
two most fundamental items of hydrologic information for a river are stage,
which is the height of the water above a reference elevation, and streamflow or
discharge, which is the total volume of water that flows past a point on the
river for some period of time. Stage usually is measured in meters, and streamflow
is measured in cubic meters per second. A gage house is the most common
structure for sheltering the various instruments used to measure stage.
A gage house (pictured at right) consists of a stilling well, dug along the
riverbank, and a surrounding shelter. Water enters the stilling well through one or
more inlet pipes and then the water in the well rises to the same elevation as the
river. The height of the water in the stilling well is determined by placing a
submersible pressure-transducer in the well or by using a mechanical float.
The transducer has a
pressure-sensitive diaphragm system that translates the pressure exerted on
the diaphragm to an electrical signal. The signal is transmitted to the data-collection platform (DCP) in the gage house.
The DCP transmits the data to the
Meteosat satellite, which in turn transmits the data to the primary ground
station in Fucino, Italy. The data then are routed to Darmstadt, Germany, and
distributed to users or retransmitted to the satellite for users to
receive directly with a reception station. The satellite data-delivery system will
operate even when extreme high water or wind disrupts normal telephone and
electrical power services.
An outside reference
gage, typically a vertical graduated ruler called
a staff gage, is read periodically to verify that the recorded gage heights
from the stilling well are the same as the water levels in
the stream. The staff gage pictured at right is the low-water staff gage under
the Borzhave River bridge at Dovhe.
