Lakes, streams, springs, snow, and ice are the most obvious source of fresh water on the North Slope. However, permafrost and seasonal climatic effects restrict the availability of these sources for water supply.

Shallow thaw lakes, ranging from the 315-mi² (815-km²) Teshekpuk Lake to ponds less than an acre, literally blanket large parts of the coastal plain. Ice-cover formation and thickening on these lakes in winter are accompanied by an increase in dissolved-solids concentration in the remaining water, thus limiting its suitability for water supply.

Most of the precipitation occurs as snow, which is stored on the land surface until it melts in late spring and summer. Snow and ice are used to construct temporary roads and airfields, and melted snow and ice are often used as potable water. Most of the annual streamflow occurs during

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a brief two- to three-week breakup period in late May and early June. Streamflow virtually ceases in all streams, including the largest rivers, during the long, cold winters.

At a few locations, ground-water supplies have been obtained from shallow thawed zones adjacent to or underlying streams. Most ground water beneath the permafrost is brackish at best. Large perennial springs such as Shublik and Sadlerochit discharge from carbonate rocks in the central and eastern Brooks Range and foothills and within the southwestern Brooks Range, but are remote from areas of present development.

The most successful water-supply developments combine the use and removal of gravel with simultaneous creation of deep surface to store abundant summer streamflow.

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