country and the major administrative, commercial, and population center. In 1993 it was linked to other towns and development sites by a system of about of paved roads. Doha's international airport has an approximately main runway, capable of receiving all kinds of aircraft. Historically, settlement distribution in Qatar has mainly been dictated by the presence of obtainable fresh groundwater. Rawdas, which are depressions with shallow groundwater, have typically been the most popular sites of settlement throughout the peninsula. In Qatar's south, where groundwater is exceedingly difficult to obtain, settlement formation was mostly limited to wadis (dry river valleys) fed by run-off from nearby hills and rawdas. Environmental agreements Qatar is currently party to the following international environmental agreements: Biodiversity Climate Change Desertification Hazardous Wastes Law of the Sea Ozone Layer Protection References Bibliography External links