Drought Cycle Analysis to Evaluate the Influence of a Dense Network of Small Reservoirs on Drought Evolution

Neto, Germano Ribeiro; Melsen, Lieke; Martins, Eduardo; Walker, David W.; Oel, Pieter van

doi:10.1029/2021wr030799

Cited by 20 publications

(24 citation statements)

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“…In dry regions, the water stored in reservoirs has a fundamental importance to supply the population's water demand during the dry seasons and droughts, as well as the use of water for industrial processes and food production by irrigation [2]. The increase in the population and the consequent growth in water demand, combined with climate and land use changes, have put pressure on water resources and increased the risk of severe hydrological droughts over the years in these dry regions [3]. The combination of strategic reservoirs with many small reservoirs in dryland catchments generates a Highdensity Reservoirs Network (HdRN) that should improve water security, but it can modify streamflows during dry and wet periods.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the construction of small and medium-sized reservoirs has intensified in recent decades. These small reservoirs (below 1 million m 3 ) are often built by the population itself or by farmers as they are essential for the availability of water in these rural communities. In addition to the importance of reducing inequality in the water distribution for water-scarcity regions, these small reservoirs have low costs [2,5].…”

Section: Introductionmentioning

confidence: 99%

“…One reason it is hard to estimate the cumulative impact of the HdRN on the hydrological processes of a region is a lack of data about small reservoirs, mainly information on storage capacity and surface area. Their mapping has grown a lot in recent years with the advancement of remote sensing techniques, which enable the acquisition of surface areas during rainy periods from satellite images combined with digital elevation models, and consequently, the estimation of storage capacities [3,5,9,10]. The spatial density of small reservoirs is quite different around the world.…”

Section: Introductionmentioning

confidence: 99%

“…For example, densities range from 0.05 small reservoirs per km 2 in Nigeria to 0.4 small reservoirs per km 2 in Myanmar [5]. However, some specific dryland watersheds reach even higher values: India has 4.2 small reservoirs per km 2 [11], while Brazil has 7 small reservoirs per km 2 [3], and Australia has 10 small reservoirs per km 2 [12].…”

Section: Introductionmentioning

confidence: 99%

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Impact of Dense Networks of Reservoirs on Streamflows at Dryland Catchments

et al. 2022

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Small reservoirs play an important role in providing water to rural communities. Increased construction of small reservoirs to mitigate the effects of droughts leads to a High-density Reservoirs Network (HdRN) of small reservoirs, which can potentially modify the streamflows both in dry and wet periods. However, there is a lack of understanding of the interannual behavior of flow retention and the impact of future increases in the number of small reservoirs, mainly for HdRN in dryland catchments. This research aims to determine the possible impact of the increase in the number of small reservoirs on dry hydrological networks, evaluating the annual flows generated at the outlet of a dryland watershed for scenarios with different densities of small reservoirs (number of reservoirs per area). The study area was the Conceição river catchment (3347 km²) in the semiarid of Brazil. The hydrological model of the study area was developed in SWAT. The model obtained appropriate results for daily streamflows, with values of 0.63, 0.81, and 0.53% for NSE, KGE, and PBIAS, respectively. The current density of small reservoirs in the region was estimated at 0.068 reservoirs per square kilometer (res/km²). Eight expansion scenarios were defined for densities between 0.1 res/km² and 3.0 res/km². The results showed that the influence of the HdRN on runoff reduction mostly occurs for a probability of exceedance between 1% and 10% of month flows and is very small for months with very high peaks of flow. The reduction in the outlet flow due to the increase in the number of small reservoirs was stronger during dry years (up to 30%) than during wet years (up to 8%), and it tended to increase in years with a consecutive lack of rain (from about 7% in the first year to about 20% in the last year and in the worst scenario), which may intensify the period of extended droughts. This research provides insights about the impact of the increase in the number of small reservoirs on the interannual variability of flow retention, and the understanding of the influence of small reservoirs on runoff reduction may help water resources agencies better prepare for hydrologic extremes (droughts and floods).

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impact of Dense Networks of Reservoirs on Streamflows at Dryland Catchments

et al. 2022

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“…However, holding back water upstream exacerbated hydrological drought downstream (van Langen et al., 2021) and the perceived increased water security that reservoir construction provided may have led to further unsustainable water use. The impact of these small reservoirs would likely be unknown in any physical examination due to uncertainty over their number and capacity; only further diagnostic testing , such as through remote sensing analysis and numerical modeling, can show that their presence can extend hydrological drought by up to 80% (Ribeiro Neto et al., 2021). What's more, de Araújo and Bronstert (2016) demonstrated that the small informal reservoirs are an insufficient treatment for smallholders as they cannot buffer long‐term droughts.…”

Section: Drought Case Studiesmentioning

confidence: 99%

Drought Diagnosis: What the Medical Sciences Can Teach Us

et al. 2022

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Drought management is currently informed by a variety of approaches, mostly responding to drought crisis when it happens. Toward more effective and integrated drought management, we introduce a conceptual drought diagnosis framework inspired by diagnostic concepts from the field of medicine. This framework comprises five steps: 1. Initial diagnostic assessment; 2. Diagnostic testing; 3. Consultation; 4. Communication of the diagnosis; and 5. Treatment and prognosis. To illustrate the need for the proposed approach, four case studies of recently drought‐affected regions were selected: the city of Cape Town, the state of California, the Northeast region of Brazil, and the Horn of Africa. Contrasting elements for these cases include the geographic extent and political boundaries, climate, socio‐economics, and the relevance of different water resources (e.g., rainfall, reservoirs, and aquifers). For each case, we identified documented practices and policies and reflected on them in terms of drought misdiagnosis or incomplete diagnosis that have aggravated socio‐economic and environmental drought impacts. A common example is the preference for technical solutions (e.g., installing infrastructure to augment water supply), rather than measures that reduce vulnerability. Analysis of these four drought case studies confirmed the anticipated need for a comprehensive approach to drought diagnosis for more successful treatment and prevention of drought. Using an analogy with medical science can be helpful toward comprehensively diagnosing droughts for a variety of contexts and assessing the effectiveness of proposed interventions. This framework can help drought managers to be more proactive in enabling drought‐affected regions to become more drought resilient in the future.

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