(19,262 km 2 ) Bear River average annual flow @ Corinne 1600M m 3 /year. (6,413 km 2 ) Weber River average annual flow @ Plain city 520M m 3 /year. (9,963 km 2 ) Provo & Jordan Rivers average annual flow @ SLC 1700 South 126M m 3 /year. (14,604 km 2 ) {no perennial streams} Study Area ! ! "#$%%&#’’( )*))) + !, + - ./ Abstract The Great Salt Lake (GSL), Utah, is the fourth largest, perennial, terminal lake in the world. The Great Salt Lake (GSL) level fluctuates due to the balance between inflows and outflows. These fluctuations are of interest whether they are high (flooding hazards) or low (economic impacts). Inflows are due to streamflow, primarily from the Bear River (54%), Weber River (18%) and Jordan/Provo River (28%). Inflows also include precipitation directly on the lake and groundwater both from the East and West sides. The only outflow is evaporation that is controlled by the climate, area of the lake that changes with level. The GSL reached historic high levels above 1284 m in 1873 and 1986. A historic low at 1278 m occurred in 1963. These fluctuations represent the integrated effect of climate and hydrologic processes as well as the dynamic interaction between lake volume, area and salinity that impact evaporation from the lake. The topographic area-volume relationship in the GSL plays a role in the system dynamics because area is a control on the evaporation outflux. This paper examines the relationships between Basin climate (precipitation and temperature), Inflows to the lake (primarily streamflow) and outflows (evaporation). The role played by the topographic elevation-area-volume relationship on lake dynamics and the correspondence between modes in volume and area distributions and peaks in the area-volume derivatives was examined. We derived, using a steady state approximation, the relationship between distributions of lake volume and lake area and the area-volume derivative from the topography/bathymetry. This analysis showed that both the topography /bathymetry and multimodality in the area distribution are required to explain the observed multimodality in the volume distribution. We also separated lake volume changes into increases in the spring (due to spring runoff) and declines in the fall (due to evaporation) and then related these volumes changes to streamflow, precipitation, and basinwide climate inputs. The results of this study improve understanding of the sensitivity of the GSL level to the interplay between topography and fluctuations in precipitation and climate and thereby contribute to knowledge on the interactions between hydrologic processes and long- term large-scale climate fluctuations. Motivation The Great Salt Lake Basin with major sub-basins. The Great Salt Lake is located in the north east of the Great Basin (upper left). that integrates climate and hydrologic inputs over the region. of the GSL’s level are of direct concern to mineral industries along the shore, the Salt Lake City Airport, the Union Pacific Railroad, and Interstate highway 80. During 1983-1986 the Great Salt Lake rose rapidly to its highest level in a hundred years and then declined quickly. A pumping project that cost about $60 million was initiated due to that event. the changes in GSL volume and fluctuations in GSL level as they are related to the inputs of precipitation, temperature and other regional measures of climate. the role of the topographic area-volume relationship in the occurrence of modes representing potential preferred states in the system dynamics, the full set of interactions between basin hydrology and lake inputs and outputs. Objectives Air Humidity Streamflow Soil Moisture And Groundwater Mountain Snow pack Precipitation Air Temp. Evaporation Solar Radiation Salinity GSL Level Volume Area Conceptual Model: Processes that drive the GSL volume fluctuations. Jordan River -#’&(#%% Utah Lake Antelope Island Bear Lake B E A R R J O R D A N R W E B E R R P RO V O R B E A R R B E AR R WEB E R R 0 30 60 15 Kilometers Utah Nevada Idaho California Arizona Oregon Sub-basin Drainage Areas Bear 19,262 km 2 Weber 6,413 km 2 West Desert 14,604 km 2 Jordan/ Provo 9,963 km 2 Salt Lake 4,713 km 2 Total 54,955 km 2