The Lake Tana basin is located in the north western part of Ethiopia. It comprises anrnapproximate area of 15,114 km2 including Lake Tana. The basin is a high touristrndestination site particularly to see old monasteries hosted by many islands and the BluernNile Fall. Lake Tana is also known by its diverse fish species. In addition to itsrnecological values the lake is used for water supply, fishing, irrigation, hydro power andrnmany other ecosystem services. However the basin is facing many threats. One of thesernthreats is change in land use and land cover. The specific objectives of this study are tornassess land use and land cover change in 1986, 2001 and 2015, and to quantify thernimpact of this change on the runoff in the basin. ERDAS IMAGINE and ARC GISrnused for land use and land cover change analysis, and SWAT model simulation forrnquantifying the impact of land use land cover change on the runoff. The major land usernand land cover types identified in the basin are farm land and settlement, shrub land,rnrange land, forest, bare land, wood land, wet land, and water body. The results of thernstudy showed that farm land is continuously increased from 34.8 % in 1986 to 44.3 %rnand 55.1 % in 2001 and 2015 respectively. Conversely wood land decreasedrnpersistently within these years. Forest cover, wet land and bare land increased betweenrn1986 and 2001 but decreased between 2001 and 2015. Shrub land and range landrndecreased initially between 1986 and 2001 but increased between 2001 and 2015.rnWater body slightly decreased between 1986 and 2001, and has the same coveragernbetween 2001 and 2015. Consequently the mean annual and wet months (JuneVrnSeptember) runoff decreased in the 2001 LULC from the 1986 LULC by 0.2 mm andrn0.6 mm respectively. This is mainly due to the increase of forest cover although farmrnland and settlement cover also increased in the 2001 LULC from the1986 LULC. Butrnthe mean annual and dry months (October-May) base flow decreased in the 2001rnLULC from the 1986 LULC by 0.8 mm and 0.7 mm respectively. Then mean annualrnand wet months (June-September) runoff increased in the 2015 LULC from the 2001rnLULC by 2.1 mm and 5.8 mm respectively. This is primarily due to the decrease ofrnforest cover, and the increase of farm land and settlement cover in 2015 LULC fromrnthe 2001 LULC. Accordingly the mean annual and dry months (October-May) basernflow decreased in the 2015 LULC from the 2001 LULC by 3.9 mm and 2.3 mmrnrespectively. The other major threat on the water resources of the basin is climaternchange. The change of land use and land cover, and climate, and their impact on thernrunoff and base flow in the basin has many implications on Lake Tana. For example, ifrnthe runoff amount increased, consequently the sedimentation to the lake will also bernincreased. Sedimentation leads to many negative impacts to the lakeâ€™s water and fishrnresources. Climate change will decreased on lake precipitation and surface waterrninflow, and increased evaporation, then the lakeâ€™s water balance will be disturbed andrnresulted in to water shortage. In the opposite on lake precipitation and surface waterrninflow will be increased although evaporation also increased, then it resulted in to lakernlevel rise and flooding which especially affects the downstream countries.