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H. Maruszczak, M. Wilgat

A. Świeca (1984) presented the percentage of components coming from municipal and industrial wasterwaters estimated for the Uherka river catchment. The first attempt at balancing the solute yield from the whole Vistula river basin was madę by H. Maruszczak (1986, 1990). In that balance — on the basis of hydrometrie data from the gauging stations at Tczew and Kieżmark in the 70’s — account was taken of the components of the solute yield coming from: precipitation, agricultural chemization, municipal and industrial wasterwaters and natural Chemical denudation. The percentage of the last component was calculated at 48%, on the basis of data from the 70's.

In this paper we present the results of balance analysis of the river solute yield from the catchments of selected tributaries, and also from the whole Vistula river basin. They were obtained in the Department of Physical Geography and Paleogeography of Maria Curie-Sklodowska University, Lublin. We used the results of analyses of the solute concentration in river water samples collected every month at control points of Provincial Centres for Studies of the Environment and its Control (about 1000 points in the Vistula river basin). These data were collected in connection with a research programme realized by several departments on "Changes of the geographical environment in Poland" (in the years 1981—1985: MR.I.25, and in the years 1986-1988: CPBP03.13). They were measurement data for the years 1976-1983. To calculate the balance, mean monthly values of discharges of waters (dm³s^-1km^{- 2}) in selected rivers in the same period were also necessary. As the results of discharge measurements were published till 1983 only, we also used unpublished archival data of the Institute of Meteorology and Water Management.¹ It should be stressed that we compiled basie data not for hydrological but for calendar years, because the records madę at Provincial Centres concem calendar years.

RIVER SOLUTE YIELD FROM RURAL AREAS

The basie materiał for calculation of the balance is shown on our map of solute yield from rural areas (Fig. 1). The isolines plotted on it illustrate indices of solute discharge estimated for smali catchments (of subordinate tributaries) in which bigger sources of municipal and industrial wasterwaters are absent.

The solute yield from these catchments was calculated in a simplified way from the formula:

1

' Most of the analytical data from the Provincial Centres for Studies of the Environment and its Control

were offered without charge; for a Few provinces we obtained the necessary data against payment from the Informatical Centre of Environment Protection and Water Management in Płock. We wish to express our gratitude to the directors of the Provincial Centres who agreed to offer the measurement data free of charge. We are also indebted to the director of IMiGW for offering without charge the unpublished data on discharges from the years 1983-85 in the rivers we studied.