The poor living conditions provided within the resettlement villages has been demonstrated by population reductions since resettlement. One resettlement village in particular experienced a greater than 50% population reduction in the 23 years following relocation. Increased economic risks and experiences of poverty are associated with those communities most impacted by the Volta River's development. The extensive human migration and degradation of natural resources within the Volta-basin area, are the products of poverty in conjunction with population pressure. Increased human migration within the area has been driven by poverty and unfavorable resettlement conditions. This migration enabled the contraction of HIV and has since led to its heightened prevalence within Volta Basin communities. The districts of Manya Krobo and Yilo Krobo, which lie within the southwest portion of the Volta Basin, are predominantly indigenous communities that have attained a disproportionate prevalence of HIV. The situation underlines the strength of the local factors upon these districts. Commercial sex work was established in response to the thousands of male workers that were in the area for building the dam. Ten percent of the child-bearing females from these two districts migrated out of their districts during this time. In 1986, "90% of AIDS victims in Ghana were women, and 96% of them had recently lived outside the country". The Akosombo Dam and other dams of the Volta River Hydro Development Project increased substantially the conditions for the spread of schistosomiasis. Reservoir-induced seismicity has been recorded due to the crustal re-adjustments from the added weight of the water within Lake Volta. There is an eastward shift of the river's mouth from the changes to the river's delta zone and this has led to continuing coastal erosion. The changes in the river hydrology have altered the local heat budget which has caused microclimatic changes such as decreasing rain and higher mean monthly temperatures. All of these larger scale environmental impacts will all further compound the problems surrounding disruptions to local economic activities and associated, difficult human welfare conditions. A case study by the International Federation of Surveyors has indicated that the dam has had a significant impact on the shoreline erosion of the barrier separating the Keta Lagoon from the sea. Dr. Isaac Boateng has calculated the reduction of fluvial sediment as being from 71 million m3/a to as little as 7 million m3/a.