Analyzing the Low Flow Trends in Northwest Indiana Using Neural Network

Abstract

This research focuses on the low flow regime of Lake Michigan watershed in the northwest Indiana, located in the southern tip of Lake Michigan. Low flow is mainly contributed through groundwater flow. Ecosystem survival depends on the low flow regime (Sala et al., 2000). Changes in landuse pattern, climate change, river training works and many other factors influences the low flow. This region had encountered lot of changes in the landuse pattern during the last 50 years. Runoff from five watersheds was used in this work. Analysis such as single station trend, regional trend, 7Q10 flow, flow duration curve and seasonal trends were conducted systematically to understand the behavior of low flow regime. Historic data such as daily flow, monthly mean temperature, monthly rainfall and land use changes were considered. To study the influence of different factors, artificial neural network based approach was used. Using relative strength effect (RSE) associated with each input neuron, the influencing factors were examined. This study indicates an increasing trend in the low flow regime for this region. BACKGROUND This research focuses on the Lake Michigan watershed located in northwest Indiana. This historic region is in the southern tip of Lake Michigan and includes a part of the southern suburbs of greater Chicago. This region had encountered many changes in the land use pattern during the last 50 years. This research mainly focuses on the low flow regime in northwest Indiana. Low flow is mainly contributed through groundwater flow. Ecosystem survival depends on the low flow regime (Sala et al., 2000). Changes in land use pattern, climate change, river training works, and many other factors influence the low flow regime. A brief review of a few essential articles is given in the next paragraph. United States Environmental Protection Agency (USEPA) publishes the 303(d) document every year and lists the impaired streams for different water quality constituents. This region has several impaired creeks. Changes in low flow regime can significantly influence the water quality. Low flow augmentation is practiced to support living organisms, to manage nutrient balance, and to avoid sea water intrusion in different parts of the world. Many researchers have presented different findings about the low flow regime. Wayland et al. (2003) examined the relationship between land use, base flow conditions, and stream chemistry. Schilling and Libra (2003) indicated that the increase in base flow was due to the presence of the large agricultural land use pattern in Iowa, where crop land covers 70% of the land area. They also indicated that from 1940 to 2000 the base flow was increased from 20 % to 30% in several Iowa rivers. Rose (1996) showed that the vadose zone drainage during cooler or wetter months can also contribute to base flow changes. Thorburn et al. (1991) indicated that forest clearing has a substantial effect on 1772