Over the three impacted time periods, the long-term median monthly flows ranged from +5.3% to −62.7%, −28.2% to −77.5%, and −23.6% to −76.8%, respectively. The annual hydrologic anomalies in median flows ranged from about −26% to nearly −82%. Results also show a sharp decline of the natural flow regime over 15 years (1999–2013). Associated impacts are clearer for the nonrainy seasons. Findings reveal that the human-related activities coupled with the impact of drought within the period between 19 have considerably modified the flow regime and therefore reduced the flow volume available for the downstream state. Man-made perturbations in the upstream country Iran have considerably changed the flow regimes in the downstream state Iraq.
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Damming and massive water withdrawals by the agricultural sector can be considered as potential drivers of hydrologic alteration. Miklas Scholz, in Sustainable Water Treatment, 2019 3.4 Conclusions and Recommendationsĭams for flood control, hydroelectric power generation, and water supply, particularly benefiting irrigation projects, have markedly contributed to the impaired flow in the Diyala river basin. An underground tunnel takes water from the high reservoir to the power generation plant built in an underground cavern near the lowest point of the water tunnel. These are used generally make use of a large natural height difference between two waterways, such as a waterfall or mountain lake. A typically setup of run-of-the-river type is without dams, but rather pipes divert some of the flow, drop water down a gradient.
Even smaller turbines of 200–300 W may power a single home in a developing country with a drop of only 1 m. HP generation capacities less than 5 kW are referred to as Pico HP plants, which may help to light small and remote communities with only a small amount of electricity requirement. These systems complement photovoltaic solar energy systems, because in many areas, water flow, and thus available hydropower, is highest in the winter when solar energy is at a minimum. Around the world there are many of such type of power plants, which is mostly preferred in developing countries, because they can provide energy economically. Their capacity for HEP generation is up to 100 kW of power and installations can provide power to an isolated home or small community, or are sometimes connected to electric power networks. Hence, environmental impact is low and depends strongly on the balance between streamflow and power production.
They usually have minimal reservoirs and they have relatively low environmental impact in comparison to large HP plants. On the other hand, their projects may be in isolated areas away from uneconomic to serve from a network, or in areas where there is no national electrical distribution network. The small HP stations may be connected to conventional electrical distribution networks as a source of low-cost renewable energy. However, in some countries this upper limit is regarded as 25 MW in Canada and 30 MW in the United States. Their definition is variable but in general 10 MW generation capacity is accepted as the upper limit of these hydroelectricity generation stations. These serve as hydroelectricity generation units to small community or individual industrial plants. Zekâi Şen, in Comprehensive Energy Systems, 2018 4.12.4.5 Small Hydropower Plants