The state of water resources in the Philippines - Greenpeace

Classification
Class AA
Waters intended as public water supply requiring only approved
disinfection to meet the PNSDW
Class A
Waters suitable as water supply requiring conventional treatment to
meet the PNSDW
Class B
Waters intended for primary contact recreation (e.g. bathing,
swimming, skin diving, etc.)
Class C
Waters for fishery, recreation/boating, and supply for manufacturing
processes after treatment
Class D
Waters intended for agriculture, irrigation, livestock watering, etc.
Table 2. Number of classified inland surface water bodies
(Source: EMB National Water Quality Status Report, 2006)
Number
5
203
149
231
23
This means that only 39 percent of the 525 water bodies may be considered as
potential sources of drinking water.
B. Water quality assessment
For the period 2001 to 2005, the EMB monitored a total of 196 inland surface
waters: 192 rivers and four lakes. Of the 196 monitored water bodies, only 127
met the required four sampling events and were included in the analysis. Data
on the status of water quality contained in the EMB National Water Quality Status
Report using each of the parameters mentioned earlier are presented below.
Dissolved oxygen (DO)
Dissolved oxygen (DO) is the amount of oxygen that is dissolved in water and is
essential to healthy streams and lakes. Dissolved Oxygen is one of the water
quality parameters used as an indication of how polluted the water is and how
well the water can support aquatic plant and animal life. A higher dissolved
oxygen level usually indicates better water quality. If dissolved oxygen levels are
too low, some fish and other organisms may not be able to survive (Stevens
Institute of Technology, The Global Water Sampling Project 2007).
Generally, the national standard for DO is 5 mg/L, except for water bodies
classified as Class D and Class SD, with standards set at 3 mg/L and 2 mg/L,
respectively (PEM, 2004).
Low DO levels may be found in areas where organic material (dead plant and
animal matter) is decaying, as bacteria require oxygen to decompose organic
waste, thus, depleting the water of oxygen. Areas near sewage discharges
sometimes have low DO levels due to this effect (Stevens Institute of
Technology, The Global Water Sampling Project 2007).
Furthermore, low concentrations of DO, when combined with the presence of
toxic substances may lead to stress responses in aquatic ecosystems because
the toxicity of certain elements, such as zinc, lead and copper, is increased by
low concentrations of dissolved oxygen (Enderlein et al., 1996).
GREENPEACE | The state of water in the Philippines 14