The Corruption of Water
The first plague affected the entire water supply of Egypt.
Parashat Vaera describes part of perhaps the most famous narrative in Jewish history--the Exodus.
Moses and Aaron were appointed as Divine emissaries to Pharaoh, demanding the release of the Israelites from the bondage of Egypt. Refused, Moses and Aaron were then tasked with bringing plagues upon Egypt, ostensibly to compel Pharaoh to release the Jewish people. The first of these plagues was the plague of blood.
Regardless of the chemical dynamics the Nile underwent during the plague of blood, it was doubtless an impressive and awful sight--the waters of the life-sustaining river running red. Not only was the Nile plagued, but in God's instructions to Moses, all the bodies of water in Egypt were affected--from the mighty river down to the water contained in vessels of wood and stone. The text specifies that the waters of the Nile were undrinkable, and the plague caused the death of all of the fish in the river. The Egyptians, bereft of their ordinary sources of drinking water, tried to dig wells beside the Nile, in an attempt to reach potable water.
They Lasted Seven Days
Midrashic sources indicate that each of the Egyptian plagues lasted seven days. In the case of most plagues, we see Moses requesting a cessation of the plague on Egypt's behalf, and the plague is subsequently removed from the land. But the biblical text gives us no such description of this plague's end. The text merely suggests that after seven days, Moses and Aaron approach Pharaoh with a warning of the upcoming plague of frogs.
The never-ending corruption of water still plagues many areas of the Global South today. Over a billion people worldwide lack access to clean drinking water which often has severe and deadly consequences. Cholera and other water-borne diarrheal diseases are among the leading causes of child deaths worldwide--greater than HIV or malaria. Indeed, they are responsible for twenty-five percent of deaths in that demographic in the Global South.
Lack of Sanitation
One of the major causes of water contamination today is lack of effective sanitation. In fact, in about a third of all African countries, less than 50 percent of people have access to toilet facilities that do not need to be emptied by hand. Similar rates plague many Asian nations such as India, Nepal and Mongolia. Those without adequate facilities often turn to a nearby river or stream for washing, cooking and disposal of human waste, making entire communities vulnerable to cholera and other diseases.
Even in areas where clean water is available, it is not necessarily easy to access. For example, near the village of Kingori, Tanzania, there is a single public tap yielding clean water for the surrounding area, shared between both the people and domestic animals. In Ingwavuma, South Africa, the residents of the rural areas surrounding the town access water through boreholes.