The Lihu`e Basin is the source of drinking water for more than half of Kaua`i\u2019s population of 58,000. But according to a recent study by the U.S. Geological Survey, the basin has experienced sharp declines in water levels and well productivity, raising concerns \u201cabout the future reliability of ground-water sources.\u201d<\/p>\n
The USGS identifies three factors contributing to the decline. First, there is increasing demand for water from the basin. Second, rainfall in the area has been lower than average in recent years. Most significant, though, is the third factor: the phase-out of sugarcane cultivation in the area. Irrigation of the cane fields, the USGS says, \u201cartificially increased recharge by about 25 percent over natural conditions.\u201d<\/p>\n
According to the lead author, Scot Izuka, \u201ceven if there was agriculture to replace sugar, they wouldn\u2019t use the inefficient, furrow-irrigation method used in the early days of sugar.\u201d Sugar planters were themselves switching from furrow irrigation to drip, which was three times as efficient \u2013 and therefore contributed much less to groundwater recharge. Also, says Izuka, \u201cwe didn\u2019t consider the effect of increased demand, since this was primarily a recharge study. We\u2019re working now on a model to see what happens when we put everything together \u2013 pumping, changes in recharge, etc. That won\u2019t be done for probably another year.\u201d<\/p>\n
\tWater levels have declined to the point that well and tunnel production has been affected. \u201cFor example,\u201d the report states, \u201cat the Garlinghouse Tunnel, one of the most productive sources of public water in the area of the Kilohana-Puhi wells, two pumps could be operated continuously prior to 1970, yielding about 1,500 gal\/min for extended periods. By the 1990s, however, only one pump could be operated (at about 800 gal\/min) without causing water levels to decline to the level of the pump intake.\u201d<\/p>\n
\tWhen the USGS put together a model of the groundwater combining no irrigation with extreme drought conditions, the result was a calculated \u201cworst-case scenario,\u201d with a decrease in recharge of up to 84 percent from the 264 million gallons a day of recharge when cane fields received furrow irrigation in a wet year. \u201cOf course, droughts are passing things,\u201d Izuka says. \u201cOne would imagine eventually they will go away and we\u2019ll have higher-than-normal rainfall to compensate.\u201d<\/p>\n
\tThe study, he says, shows the extent to which irrigation can have a substantial effect on recharge. \u201cWe haven\u2019t done studies like this in every area where there used to be sugar, but it would be interesting to do that.\u201d<\/p>\n
\tThe report\u2019s conclusions do not bode well for the area served by the Lihu`e Basin. \u201cResults of the water-balance analysis indicate that recent variations in precipitation and irrigation in the Lihu`e Basin have caused large reductions in ground-water recharge, and that plausible scenarios of future land-use changes and drought could result in even greater reductions in ground-water recharge.\u201d<\/p>\n
\t(The report, \u201cEffects of Irrigation and Rainfall Reduction on Ground-Water Recharge in the Lihue Basin, Kaua`i, Hawai`i,\u201d was written by Scot Izuka, Delwyn Oki, and Chien-Hwa Chen. It is available online at [url=http:\/\/pubs.usgs.gov\/sir\/2005\/5146]http:\/\/pubs.usgs.gov\/sir\/2005\/5146[\/url].)<\/p>\n
— Patricia Tummons<\/p>\n
Volume 16, Number 11 May 2006<\/p>\n","protected":false},"excerpt":{"rendered":"
The Lihu`e Basin is the source of drinking water for more than half of Kaua`i’s population of 58,000. But according to a recent study by the U.S. Geological Survey, the basin has experienced sharp declines in water levels and well … Continued<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[135],"tags":[],"class_list":["post-1449","post","type-post","status-publish","format-standard","hentry","category-may-2006"],"_links":{"self":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/posts\/1449","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1449"}],"version-history":[{"count":0,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=\/wp\/v2\/posts\/1449\/revisions"}],"wp:attachment":[{"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1449"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1449"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/environment-hawaii.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1449"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}