THE ROLE OF IRRIGATION IN RIVER VALLEYS TO DEVELOP WATER QUALITY, PRODUCTION OF BIOMASS AND SUSTAINABLE RURAL DEVELOPMENT - CASE STUDY

Abstract

Ner river and its valley for over 170 years has been receiver for sewages from the city of Łódź. The natural system of this region (on the border of the watershed location, limitations of water supplies sources, lack of bigger natural rivers) in connection to city growth, lead to forming of specific system involving an agglomeration and water supplies system as well as wastewaters utilization system. The Ner river valley has the great potential to be effective in production biomass for energy purposes. Irrigation with polluted Ner river water cover fast growing plants high water and nutritional requirements. This would also work for the improvement of Ner river water quality. The achievement of good quality of water is not possible without irrigation of agricultural land in river valley. An amount of sewage discharged to Ner (193,017 m³ per day) several times higher then its natural flow in river. This is a result of strategy of water supply that is supported by transfer of water from Pilica river and underground water uptake for agglomeration. Relatively high runoff coefficient in years 1952 – 2011 was equal to 0.325 for Ner, in comparison to 0.17 for other rivers in Warta watershed. Despite the low natural flow Ner river discharges annually relatively high contaminants’ load to Warta river. In the analysed period (1995-2003) the annual average flow of Ner river amounted 10 % of annual average Warta river flow below its estuary. The share of analysed indicators of contaminants’ load approximated 27 % for total nitrogen, 37 % for phosphorus, 39 % for BOD5 and 28% for suspended solids. In the period 2004-2011 the annual average flow of Ner river amounted 13.8 % of annual average Warta river flow. The share of investigated pollutants loads consists 27.9 % for total nitrogen, 42.6 % for phosphorus, 19.8 % for BOD5 and 19.6 % for suspended solids.