Any doubt that California is hip-deep in an epic struggle for water was put to rest earlier this month when an estimated 10,000 farmers and farmworkers marched 50 miles across the gasping San Joaquin Valley.

The goal was to heighten awareness about their water shortage, brought about by a third year of drought in California and environmental problems in the Sacramento-San Joaquin Delta. Their alliance is surprising, given a long history of acrimony between farm owners and laborers. It demonstrates the shifting alliances and simmering tensions that emerge when people fight over water.

We're likely to see more struggles over water, both locally and worldwide. The next big conflict in California is a proposal for a canal built around the Delta, designed to secure a water supply for Central Valley farms and Southern California cities while also improving the environment of the West Coast's largest estuary. Critics worry that it's simply a tool to drain the Sacramento River.

Preventing a water grab paradoxically requires us to set aside turf battles and focus instead on how the so-called peripheral canal will be managed. Who will be in charge of turning the water valves on and off? When and why? These questions, more than how much water is transferred south, hold the solution to managing future shortages.

In coming years, 46 nations risk violent conflict over water and climate-related crises, and 56 other countries face political instability, according to a study by International Alert, a British advocacy group. The United Nations says water wars may be more likely in the future than wars over oil.

"Water will … become one of the defining limits to human development and a compounding factor in human misery," Achim Steiner, director of the U.N. Environment Programme, said during the World Water Forum, attended by more than 30,000 government officials and nonprofit leaders last month in Istanbul, Turkey.

A key message at the forum: There is probably enough fresh water available to meet human needs, despite climate change and population growth. However, the problem is poor management of water, which results in scarcity and conflict.

Fights over water – some small, others as large as California – are occurring across the globe. I recently visited a rural area in Ethiopia, where a breach of trust left two villages without a secure water future.

Near the mountainous town of Ticho, about three hours south of Addis Ababa, a group of villagers washed clothes and gathered water at a natural spring. Many filled ubiquitous "jerry cans" – 6-gallon yellow plastic jugs used to fetch water from creeks or public taps.

As we approached, an older man ran up shouting and gesturing for us to leave. He accused us of coming to steal the springwater, we learned through our translator.

The banks of the spring, deeply shaded by trees, were littered with animal feces, the water cloudy and gray. A half-finished wall surrounded the spring – an effort to cap the source and pipe the water to two villages. A contractor had been hired by the state government to develop the spring to serve his nearby village and another, 37 miles away.

Once construction began, the locals learned that all the water would go to the distant village. They would get none. So they kicked out the contractor, halted the project and drove away a state official who later tried to negotiate a compromise. They told us the spring was holy and refused to let us take pictures or talk to anyone from the village.

"If I were them, I would too," said Shibabaw Tadesse, a local coordinator with WaterAid, a British charity that funds projects in Ethiopia. "Such kind of resource cannot be capped. It's amazing, really. Amazing."

An apparent bungling of the construction contract – a case of mismanagement – sowed the seeds of distrust.

In the San Joaquin Valley, where 40 percent of America's produce is grown, farmers have been told they'll get only 10 percent of their contracted federal water supply this year. Cities in the Bay Area and Southern California, which receive water from the state, expect only 30 percent of normal deliveries. UC Davis economist Richard Howitt predicts losses of at least 40,000 farm-related jobs and $1.15 billion in income. Thousands of acres of crops have already been fallowed.

Matt Weiser covers water and natural resources for The Bee. His trip to Istanbul and Ethiopia in March was funded by Media21, a journalism foundation in Geneva. Contact him at (916) 321-1264.