The uncontrollable dumping of raw sewage from point and non-point sources becomes the major contributor of water quality degradation of most river basins. Only 70% of the total garbage generated daily is being collected for proper
waste disposal. Uncollected wastes end up mostly in rivers and their tributaries causing pollution of major water bodies in the country.
Highly polluted water bodies result to numerous catastrophic effects not only to the whole water ecosystem but also to public health. The capacity of waterways to sustain habitat for aquatic organisms has been severely reduced because of the reduction of BOD levels needed by them. Likewise, contaminated water sources decrease water supply and might create threats to flooding due to clogged waterways.
River rehabilitation is therefore necessary to partially restore degraded form of waterways caused by waste contamination. Rehabilitation is a process of partial functional and structural return of degraded water bodies into former pre-degraded condition by putting them back to good working order. It is dedicated to the ecologic state by structural and non-structural measures.
River rehabilitation embraces a great variety of measures giving emphasis on natural functions of rivers which may have been lost or degraded by human intervention. The adaptation of dredging practices is necessary to clear out solid wastes and improve channel capacity to prevent flooding. Relocation of informal Settler Families (ISF) inhabiting along riverbanks and esteros of some heavily populated communities must be implemented to initiate the rehabilitation process. BOD and COD levels are also measured as baseline for water quality improvement.
The inclusion of vegetation along with rehabilitation measures greatly contributes to the partial restoration of river biodiversity. Plants play a significant role in phytoremediation. Aquatic plants become the effective nutrient sinks and absorbers of organic and inorganic pollutants.
River bioengineering offers effective and immediate solution to establish vegetation along degraded riverbanks. Bioengineering, in combination with civil engineering techniques, stabilizes embankments necessary to grow vegetation in the banks. Bare embankments must be protected to secure newly planted grass against erosion.
Floating wetlands with aerators may also be used to improve water quality of the river. Aeration provides oxygen needed by aerobic bacteria for the decomposition of suspended organic wastes. Roots of aquatic plants in wetlands serve as habitat for these microorganisms during the decomposition process.