Surface water

The text is based on the chapter Surface water published in yearbook Prague Environment 2005.

(the text below is based on the chapter Surface water published in yearbook Prague Environment 2005)

The water quality assessment is every year performed according to the Czech Standard TNV 75 7221 “Classification of Surface Water Quality”. The standard was made more exact on the basis of experience of its practical use and at the same time it was closer harmonised with the surface water classification, which is in use in the EU Member States. The standard is focused on the uniform determination of quality class of flowing surface water – the classification, which serves for benchmarking of water quality at various locations and in various times. Surface water is classified into five classes based on quality. Water quality is classified on the basis of check results acquired over a longer continuous period. The shortest period assessed is one year. It is recommended, at monitoring frequency of 12 samples taken per a year, to make the classification of the check results for a two-year period in order to have 24 values measured (1999–2000), at least, for the characteristic value calculations. If there are less than 11 values – results of water quality checks – the classification pursuant to the aforementioned standard cannot be carried out. Surface water quality is then classified for each indicator separately. The assessment indicators evaluated are sorted into five groups. The indicator of the worst quality determines the entire group value. Then the group of the indicators of the worst classification value determines the overall classification of quality of water in a particular watercourse.

Tab. Surface water quality classes according to the TNV 75 7221

Class number	Classification
I.	Unpolluted water
II.	Slightly polluted water
III.	Polluted water
IV.	Heavily polluted water
V.	Very heavily polluted water

Tab. Groups of surface water quality indicators according to the TNV 75 7221

Group	Indicators
A	General physical and chemical indicators
B	Specific organic substances
C	Metals and metalloids
D	Microbiological and biological indicators
E	Radiological indicators

Water quality assessment at hydrometric profiles of the National Network on the territory of the City of Prague and in its closest vicinity

In 2004 there were 319 hydrometric profiles of the National Network on water courses monitored.

Fig. Monitored hydrometric profiles of surface watercourses – classes of water quality in the groups of indicators

Source: ČHMÚ, Lesy hl. m. Prahy, MHMP

Tab. - Regularly monitored hydrometric profiles on water courses

On the Prague territory and in its closest vicinity there were four hydrometric profiles monitored in total at the Vltava River and the Berounka River; on the Vltava River – Vrané nad Vltavou, Podolí, and Libčice, and on the Berounka River – Lahovice. Selected indicatros have been measured continuously since as early as 1963. In 2004 105 substances were measured at the profiles. The highest number of the indicators was measured at the profile Vltava – Vrané and Vltava – Libčice, 82 substances at the profile Vltava – Podolí, and 57 substances at the profile Berounka – Lahovice, mostly monitored at frequency once per month.

When assessed by the Czech Standard TNV 75 7221 the classification in chlorophyll was the worst indicator. At the profiles of Vltava – Libčice and Berounka – Lahovice its value reached class V, at the rest of the profiles it fell in class IV. The content of BOD₅ was also evaluated to be of class IV at the profile of Berounka – Lahovice and the content of lead at the profile Vltava – Podolí reached the same value. At all profiles the indicators of total phosphorus, AOX, and TOC fell within class III. The best assessment was found in the indicator called “specific organic substances”, which fell into class I in most cases, and in the indicator of total PAHs that fell into class II.

The profile Vltava River – Vrané was the profile which attained the best assessment because almost two thirds of 37 indicators measured fell within class I only, 10 indicators were in class II, three indicators were in class III, and solely one indicator – chlorophyll was classified to be in class IV.

At the profile Vltava River – Podolí assessment of class I was determined for 19 indicators out of 37 measured, 11 indicators fell in class II, and five indicators were in class III, except for the aforementioned total phosphorus, AOX and TOC, these were cadmium and zinc. Lead attained class IV the same as chlorophyll. No indicator fell in class V there.

The profile Vltava River – Libčice demonstrated the least good assessment out of these four profiles. Only 15 indicators of 37 fell in class I, 13 substances reached limits of class II, eight indicators fell in class III – total phosphorous, AOX, TOC, COD_Cr, BOD₅, ammonia nitrogen, zinc, and faecal coliform bacteria. None of the indicators reached class IV and chlorophyll was classified into class V.

At the profile Berounka River – Lahovice 35 substances were monitored of those listed in the standard TNV 75 7221. Eighteen of the indicators met limits for class I, 10 for class II, and five substances were classified in class III – total phosphorous, AOX, TOC, COD_Cr, and cadmium. BOD₅ fell in class IV and chlorophyll in class V.

The number of substances enlisted in the Order of the Government of the Czech Republic No. 61/2003 Code and measured at respective profiles was from 66 at the profile Vltava – Libčice to 54 at the profile Berounka – Lahovice. While assessing profiles pursuant to the Order immission limits for surface water were exceeded for total phosphorous, IM 105 °C, and pH at all the profiles. The limit values were most frequently exceeded at the profile Vltava – Libčice for 11 indicators out of 66 measured. The purist one of these profiles was the profile Vltava – Vrané where over 90 % substances measured were compliant with the required immission limits.

The figures demonstrate course of annual concentrations (annual values of C95) of selected substances from 1995 through 2004 against the immission limit values for surface water set in the Order of the Government of the Czech Republic No. 61/2003 Code.

Fig. The course of annual values of C95 of some of substances against the limit values set in the Order of the Government of the Czech Republic No. 61/2003, 1995–2004