Water-quality assessment of the cimanuk watershed

R. T. M. Sutamihardja and Herman Haeruman Js.

Data on water quality [physical' chemical, and biological) of the Cimanuk watershed were collected directly from the field on two occasions, namely in January and September 1978. To support this primary data, secondary data were also collected, including the geological, topographical, climatological data, and also data on demography and land use (including industrial use).

Determination of sampling sites was based on the following criteria:

1. altitude
2. land condition
3. main stream and sub-stream
4. distance from transportation facilities

The parameters of water quality were analyzed in the field laboratory in situ, and the rest of the data were analyzed in the laboratories of Bogor Agricultural University and DPMA Bandung.

The Cimanuk watershed covers an area of more than 400,000 ha and is situated between 107°25' and 108 25' east longitude, and between 6 10' and 7° 30' south latitude. The Cimanuk watershed area could physiographically and topographically be divided into three regions:

1. the upper region (consisting of the upper Cimanuk sub watershed, Cipeles sub-watershed, and Cilutung subwatershed)
2. the central region (central Cimanuk sub-watershed)
3. the lower region (lower Cimanuk watershed)

The upper region has a type A climate, the central region type B, and the lower region type C. In 1977 the population density in the upper region was 450.13 persons/km², whereas for the central region and lower region the figure was 1109.05 and 323.78 persons/km², respectively. With regard to year the total population of the Cimanuk watershed was 2,296,254 (in 1971) and 2,359,345 (in 1977) with an average population density of 551.36 persons/km² in 1971, and 556.51 persons/km² in 1977, resulting in a population rate of increase of around 2.75 per cent during the six-year period.

The water debit of the upper region during the rainy season was one to three times as high as the levels during the dry season, whereas in the lower region the same parameter during the rainy season was six to ten times that in the dry season. The temperature of water in the upper region ranged between 15° and 19°C, and in the lower region between 20° and 29°C. Flooding is still a serious problem in the Cimanuk watershed during the rainy season, in contrast to the problem of water deficiency during the dry season.

Water temperature of the Cimanuk streams was found to be naturally normal, and no signs of thermal pollution were detected which could endanger the lives of aquatic organisms. Suspended solids were the main physical pollutant, especially during the rainy season. The suspended solid content of the Cimanuk River during the rainy season was 20 to 60 times as high as the level during the dry season. The suspended solid content of the Cipeles River during the rainy season was found to be 35 to 180 times the level during the dry season. The same parameter for the Cikamiri and Cikeruh rivers during the rainy season was 60 times the level during the dry season. The suspended solid contents of 2055.4 - 3907.4 g/l during the rainy season and of 36.2 - 173.1 g/l during the dry season were an indication of a quite high level of soil erosion in the Cimanuk watershed.

The dissolved salt (indicated as salinity and conductivity) content and its SAR level showed that water from the streams of the Cimanuk watershed was still suitable for fishery, agricultural, and domestic use. This was also true of the pH level.

From the standpoint of alkalinity, the hardness and the calcium content, the water of the Cimanuk watershed may be classified as having a hardness of medium to high grade. The levels of these parameters, however, were still below the critical threshold for domestic, agricultural, fishery, and industrial use.

The dissolved oxygen content of the observed streams was found to be still within the feasibility range for aquatic organisms, especially fish. This was due to the lotic type of the observed water with its turbulency current, which made it possible for the oxygen from the air to diffuse into the water easily.

At the observation stations of Ciseureupan and Limbangan during the rainy season, the ammonia-N content of the streams of the Cimanuk watershed was found to be still within the feasibility range for fish. For drinking water and as a raw-water supply, however, the water should first be treated, e.g., by boiling.

The chlorine content of the observed water was found to be below the threshold level for fish, except at the observation stations of Samarang and Tolengas during the rainy season. This was possibly due to the chlorine-containing pesticides frequently used in agricultural areas, which were carried by the run-off during the rainy season. This presumption was based on the fact that the areas in the vicinity above the observation stations were used for dry-land agriculture and for intensive sawah culture as well.

The organic substance (BOD and TOM) content showed that the streams of the Cimanuk watershed already carried low to medium levels of organic pollutants.

The MPN-Coliform level showed that the streams of the Cimanuk watershed were already polluted by human and animal excrement and also by home domestic wastes. The MPN-Coliform density (TPC/ml = 1.1 x 105 and MPN-Coliform = 1.1 x 105 per 100 ml) far exceeded the level recommended for water for public use (MPN-Coliform = 103 per 100ml).

From the data obtained from the brief survey on water quality of the Cimanuk watershed, it could be concluded that the streams of the watershed:

1. were already polluted by suspended solids of medium to severe levels;
2. were already polluted by organic matter (including excement of human and animal origin) of low to medium levels;
3. had Fe and Zn contents, at some places also a Ci content, which exceeded the maximum limit for drinking water;
4. could no longer be used for drinking water or drinking water sources without certain treatments; this is also true of water used for industrial purposes, for cooling, or for water processing; and
5. had a water quality which was found feasible enough for agricultural and fishery uses.

References

APHA 1975. Standard methods for the examination of water and waste water. 14th ed. APHA Inc., New York.

Dent et al. 1977. Detailed reconnaisance land resource survey Cimanuk watershed area.

Pescop, M. B., 1973. Investigation of rational effluent and stream standards for tropical countries. AIT, Bangkok.

Team Kualitas Air Pusdi PSL-IPB and Proyek Pengelolaan Sumbersumber Alam Lingkungan Hidup Panitia Perumus den Rencana Kerja Bagi Pemerintah Di bidang Lingkungan Hidup 1978. A Study on the Determination of Criteria for the Quality of Water and Biotic Environment of the Cimanuk Watershed.

World Health Organization 1963. International standard for water supplies. WHO Monograph, Geneva, 2nd ed.

Discussion

Thayib: Surely the standard required for drinking water should follow WHO standards.

Sutamihardja: True, but the people have to drink whatever water is available.

Punjanan: Is it possible to determine the distance of penetration of sea water into the Cimanuk River by using salinity data?

Sutamihardja: Sampling was only in fresh water, so salinity was not analyzed.