INTRODUCTION

Fresh water ecosystems are fragile and form the key foundation elements for the social, cultural and economic wellbeing of human race. Fresh water ecosystems namely rivers, lakes, floodplains, wetlands, and estuaries provides necessary goods and services as clean food, water, fiber, energy and supporting benefits supporting the economy and livelihood that are necessary for human health and wellbeing [1]. The increasing fresh water demands and large scale withdrawal from the fresh water ecosystems for meeting various societal needs such as domestic, irrigation, industrial, power, etc., have led to large scale compromise and degradation in the natural flows conditions across India and World [2].  Harnessing rivers /streams for irrigation, drinking etc. is associated with greater cost [3] i.e., due to human centric planning for utilization of water have not taken into consideration the need of water for the aquatic, terrestrial and riverine ecosystems that support native species and sustained ecosystem that provided important goods and services. These natural flow regimes determines the quality as well as health of the river and flow regime is the primary driving force that influences riverine and aquatic ecosystems, habitats, spices richness and diversity, river morphology, biotic life, river connectivity. Based on the premise that the health of the river deteriorates if the flow is below a threshold the concept of minimum flow in rivers came into practice in 1970s, many studies since then led to the understanding of the need of various elements of natural flow regime. The concept of environmental flow helps to understand, check the negative impact of large scale withdrawals of water from a natural system, and gives an idea the minimum flow to be maintained to sustain ecology and biodiversity, which is referred as Environmental Flows. This is necessary to maintain the health and biodiversity of water bodies, including rivers, coastal waters, wetlands (mangroves, sea-grass beds, floodplains) and estuaries [2, 4, 5].
The ecological flow has been investigated in many countries and also across countries such as China [6], India [7], Spain [8], Tanzania [9], Korea [10, Russia-China-Kazakhstan [11], South Africa [12], etc. Assessing environmental flow in rivers ranging from simple approaches based on limited data to highly complex and intensive approaches involving multidisciplinary studies involving experts from various domains namely ecology, hydrology, lithology, etc. these methods [13, 14, 15] can be further classified under four sub categories namely Hydrological method, Hydraulic rating method, Habitat simulation method and Holistic method.
Analysis of Environmental flow in streams and rivers are necessary to ensure that the need of humans and that of environment are met, based on which other potential users such as industries etc., can be accommodated to abstract water [12], in determining the health of river, manage flow and protect the water bodies and river networks [6], maintain and enhance the ecological character and functions of floodplain, wetland and riverine ecosystems that may be subject to stress from drought, climate change or water resource development [17, 18].
Study of water resource availability to cater the demands based on the ecological flow and domestic requirements in each of the river basin is carried out by integration of the hydrological model with a water balance model and remote sensing data into a GIS [18, 19]. Remote sensing techniques [20, 21, 22] have advantages such as wider synoptic coverage of the earth surface with varied temporal, spatial and spectral resolutions. Classifications of these data through already proven classification algorithms [23, 24, 25, 26] provide land use information. Land use information derived from remote sensing and GIS, is integrated with the hydro-meteorological information to study the role of landscape on local hydrology. Role of Landscape dynamics along with Hydro-meteorological studies has been carried out at a larger scale at in various parts of the country such as Krishna basin [19, 27], Western Ghats [25, 28], Cauvery river basin [29] etc., using the satellite based inputs and other associated parameters such as rainfall, runoff, evaporation, transpiration, ground water monitoring and so on in determining famine, drought, cyclones, silt, flood monitoring etc that helps in defining the carrying capacity in each river basin [30, 31, 32, 33, 34, 35].
The objective of this communication is to understand the role of landscape on surface and subsurface hydrological variations across seasons by continuous monitoring of selected wells, rivers and streams of select catchments in Sagara Taluk of Shimoga District, Karnataka.