THE IMPACT OF FARMING ACTIVITIES TO WATER QUALITY OF RIVER AND LAKE RAWA PENING (Case study in Semarang Regency, Indonesia)

Abstract

ABSTRACT Fertilizer is essential substance in agricultural activities around Rawa Pening Lake. However, it has caused water pollution in water bodies around the lake. This study was conducted to measure water quality parameters, especially the concentration of the potassium, nitrate and phosphate in the water of 6 input rivers of Rawa Pening Lake and in water hyacinth plant in the lake to see the impact of fertilizers use in rice fields around these watersheds to water quality. This was a quantitative research. Samples of water from five different locations in the 6 input rivers and also water hyacinth from five different locations in the lake were taken during this study to be analyzed in the laboratory to get the concentration and load of (N), (P) and (K) in these waters and in water hyacinth in the lake . What this study found was that among the six input rivers the highest concentration of (N) was found in Parat River (0.60 mg/l), (P) in Kedungringin River (0.29 ) and (K) in Torong River (2.48 mg/l). The total load of (N), (P) and (K) found in the output river (34,860 kg, 17,511.6 kg and 14,430 kg/season respectively) were lower than the total load of (N), (P) and (K) from the input rivers (17,308.8 kg, 2,554.8 kg and 11,869.2 kg/season respectively). This means that some amount of (N), (P) and (K) substances simply stayed and accumulated in the lake water (17,551.2 kg, 14,956.8 kg and 2,560.8 kg of (N), (P) and (K) respectively. From these amount of nutrients accumulated in the lake’s water every season water hyacinth plant in the lake had in total absorbed around 73,560 kg of (N) 18.02kg of (P) and 21,120 kg of (K). One recommendation which can be put forward here is for the farmers around the lake to reduce their fertilizers usage which can be absorbed by water hyacinth plant in the lake and compensate it by utilizing water from these input rivers which had already contain some amount of nutrients. Keywords: Rawa Pening Lake, potassium, nitrate, phosphate, eutrophication ABSTRAK Penggunaan pupuk sangat penting dalam pertanian di sekitar Rawa Pening. Sayangnya hal ini mengakibatkan polusi di perairan sekitar danau. Penelitian ini dilakukan untuk mengukur parameter-parameter kualitas air, terutama konsentrasi kalium, nitrat dan fosfat di 6 sungai yang mengalir ke Rawa Pening dan di tanaman eceng gondok di danau, untuk melihat pengaruh penggunaan pupuk di areal persawahan sekitar sungai terhadap kualitas air. Studi kuantitatif ini dilakukan dengan mengambil sampel air dari lima lokasi berbeda di masing-masing enam sungai input dan sampel tanaman eceng gondok dari lima lokasi berbeda di Rawa Pening agar bisa dianalisia tingkat konsentrasi (N), (P) dan (K) di laboratorium. Beban (N), (P) dan (K) juga dihitung. Penelitian ini menemukan bahwa diantara enam sungai input konsentrasi (N) tertinggi ditemukan di Sungai Parat (0,60 mg / l), (P) di Sungai Kedungringin (0,29 mg/l) dan (K) di Sungai Torong (2,48 mg / l). Total beban (N), (P) dan (K) yang ada di sungai output (17,308.8 kg (N), 2,554.8 kg (P) dan 11,869.2 kg (K) per musim) lebih rendah dari total beban (N), (P) dan (K ) dari sungai-sungai input (34.860 kg (N), 17,511.6 kg (P) dan 14.430 kg (K) per musim. Ini berarti sejumlah (N), (P) dan (K) tinggal dan terakumulasi dalam air danau (17,551.2 kg (N), 14,956.8 kg (P) dan 2,560.8 kg (K). Dari jumlah akumulasi nutrisi dalam air danau ini tanaman eceng gondok di danau itu secara total telah menyerap sekitar 73.560 kg (N) 18.02 kg (P) dan 21.120 kg (K). Salah satu rekomendasi yang dapat diajukan di sini adalah agar para petani di sekitar danau mengurangi penggunaan pupuk mereka yang dapat diserap oleh tanaman air eceng gondok di danau dan menggantinya dengan memanfaatkan air dari sungai-sungai input yang sudah mengandung nutrien. Kata kunci: Rawa Pening Lake, kalium, nitrat, fosfat, eutrofikasi