Monitoring streamflow can potentially be used to study the impact of climate change on water resources, help understand trends of natural hazards, e.g, flash floods, cloudbursts, landslides, rockslides and avalanches, and can be applied for the assessment of freshwater services or water retained by different landscapes (Table 1) (Naithani et al. Streamflow, in developed nations, is being monitored since late nineteenth century for better management and allocation of water resources (Barrows 1998), while in developing countries, streamflow monitoring is largely understudied. There is substantial uncertainty in trends of hydrological variables due to large regional differences and limitations of the spatio-temporal monitoring networks (Bates et al. The alteration in the hydrological regime is considered as a major factor contributing to the loss of biological diversity and ecological functioning of aquatic ecosystems (Bunn and Arthington 2002 Dale et al. The availability of water affects the natural process such as the ability of soil to retain and purify water, frequency and rate of recharge, which eventually changes the local or regional vegetation type. This may also be affected by seasonality, frequency, duration, magnitude and timing of flow events (Beavis et al. Change in water regimes can occur due to decreased or increased availability of water through precipitation, runoffs, groundwater recharge and discharge. Alteration in the natural systems due to human or natural activities may affect the hydrological regime, which in turn affects the ecosystem level processes that affect the availability of water resources (Vogel et al. Considering the importance of freshwater systems to human well-being, natural processes and properties that maintain freshwater ecosystems need to be monitored at both local and global scales (Karr 1991 United Nations 2011). Freshwater plays multiple roles as supporting, regulating, provisioning and recreational services (Millennium Ecosystem Assessment 2005 Smith et al. The availability and distribution of freshwater is of grave concern, since only 2.5% of it covers the earth’s surface, only a fraction of which is accessible via lakes, reservoirs and river systems (Berner and Berner 2012). Our review suggests that the selection of a method for monitoring streamflow may be based on volume of the stream, accuracy of the method, accessibility of the terrain and financial and physical resources available.

In flat terrain, the float method is best suited for smaller streams for its operational ease and cost effectiveness, whereas, for larger streams, the particle image velocimetry may be used for its accuracy. Although comparatively expensive, the weir and flume methods are suitable for long term studies of small hill streams, since once the structure is put in place, it yields accurate results. On the basis of the strengths and weaknesses of each of the methods reviewed, we conclude that the timed volume method is apt for hilly terrain having smaller streams due to its operational ease and accuracy of results.

their applicability across different terrains and size of the streams, operational ease, time effectiveness, accuracy, environmental impact that they may cause and cost involve in it. We reviewed available methods for monitoring streamflow on the basis of six criteria viz.

Monitoring of streamflow may help to determine the optimum levels of its use for sustainable water management in the face of climate change.

Flumes