As for the market, when it approaches water it meets all sorts of obstacles: water is difficult to move, difficult to measure, difficult to price and often difficult to charge for, since many people think it should be free.
TOHL, a start-up that produces flexible piping that can be deployed from helicopters to distribute water in difficult-to-reach areas or disaster zones, says it has spent the money on things such as testing its new system with a Chilean mining company and acquiring a patent.
Second, the issue of combined sewer overflows is one of the most difficult water-quality issues faced by cities with old infrastructure like New York City.
These changes are making water supply and quality more difficult to obtain, affecting runoff and soil moisture, increasing water temperatures, decreasing snowpack and lake and river ice, threatening fish and aquatic species, and allowing saltwater intrusion and sea level rise.
Monitoring the soil's water content is not only difficult, but tedious.
It is spread through infected faeces and, once it enters the water supply, it is difficult to stop - especially in a country like Haiti which has almost no effective sewage disposal systems.
"King tides and sea surges are floodling the island to a knee high and it is difficult for the salt water to dry up, " says Ursula Rakova, a Carteret islander and campaigner.
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With no running water in the house, it was difficult to wash or dry laundry in the winter.
Ships are known to strike right whales, partly because the black creatures are difficult to spot on the water.
With the water level critically low, it is difficult to see how the turbinated flow of the dam is reaching the high levels that the state agency is claiming.
Complicating matters, Mexico's oil output has slipped to 2.55 million barrels a day from a peak of 3.4 million in 2004, as easy oil in the Gulf is replaced by more difficult reserves of deep-water oil and heavy oil onshore.
It's very difficult to bring up enough cold water in two to three days to have much effect.
He said the fire had been "extremely difficult" to tackle because of limited water supplies.
These changes are difficult to plan for, as past water patterns can no longer be used to predict the future.
There are few people to handle difficult cross-regional topics such as water resources or climate change, and few linguists fluent in tongues helpful beyond Asia.
"Currently, the Navy uses dolphins or divers feeling with their hands in such difficult conditions as near-shore bubbly water, for example in the Gulf, " he said.
There is a great possibility that the reactor will be decommissioned as the injection of sea water containing salt and impure substances will make it difficult to operate it safely again, experts say.
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On the water at night, the flies get so thick it is difficult to see.
Oil is what economists call a "fugitive resource, " a thing, like water or wild game, that migrates where it wants and is difficult to own in any conventional sense.
The infection hides in the intestine and lymph nodes and can survive in manure and pond water for a year or more, making transmission of the disease difficult to stop.
And as the international markets increasingly see sterling as a 'safe haven' in uncertain times, the prospect of a strengthening pound would make it even more difficult for local exporters to sell their goods across the water.
Nothing quite matches Hong Kong from above, but it is difficult to get things wrong with mountains on one side, water on the other and skyscrapers in the middle to provide the platform.
She says she chose Lake Ontario for her swim because it's one of the hardest open-water swims in the world, and she wanted to "accomplish something difficult" for children who fight cancer.
Salt-water mosquitoes have a range of 100 miles and that's making tracking their breeding site difficult.
Like many maternity clinics in rural parts of Africa, the health center in Atitiri is lacking several necessary resources -- shortage of running water, electricity challenges, broken beds and scarcity of medicines all make Madudu's job very difficult.
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Making a jumping robot is difficult because the downward force needed to propel it into the air usually pushes the legs through the water's surface.
ENGADGET: Chinese microbot walks on water, skims the surface of insect-inspired design
New water heading into the river was shut off Thursday night, slowing down its flow, but the task nonetheless remained difficult.
But with the last couple years being so difficult for jobs, why are budget cuts to programs that are helping these people keep their heads above water?
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