Spatially distributed impacts of climate change and groundwater demand on the water resources in a wadi system

Understanding current and possible future alterations of water resources under climate change and increased water demand allows for better water and environmental management decisions in arid regions. This study aims at analyzing the impact of groundwater demand and climate change on groundwater sustainability and hydrologic regime alterations in a wadi system in central Iran. A hydrologic model is used to assess streamflow and groundwater recharge of the Halilrood Basin on a daily time step under five different scenarios over the baseline period (1979–2009) and for two future scenario periods (near future: 2030–2059 and far future: 2070–2099). The Indicators of Hydrologic Alteration (IHA) with a set of 32 parameters are used in conjunction with the Range of Variability Approach (RVA) to evaluate hydrologic regime change in the river. The results show that groundwater recharge is expected to decrease and is not able to fulfill the increasing water demand in the far future scenario. The Halilrood River will undergo low and moderate streamflow alteration under both stressors during the near future as RVA alteration is classified as “high” for only three indicators, whereas stronger alteration is expected in the far future, with 11 indicators in the high range. Absolute changes in hydrologic indicators are stronger when both climate change and groundwater demand are considered in the far future simulations, since 27 indicators show significant changes, and the RVA shows high and moderate levels of changes for 18 indicators. Considering the evaluated RVA changes, future impacts on the freshwater ecosystems in the Halilrood Basin will be severe. The developed approach can be transferred to other wadi regions for a spatially distributed assessment of water resources sustainability.

Numerical assessment of climate change impact on the hydrological regime of a small Mediterranean river, Lesvos Island, Greece

Frequency of flash floods and droughts in the Mediterranean climate zone is expected to rise in the coming years due to change of its climate. The assessment of the climate change impact at a basin scale is essential for developing mitigation and adaptation plans. This study analyses the variation of the hydrologic regime of a small Mediterranean river (the Kalloni river in Lesvos Island, Greece) by the examination of possible future climate change scenarios. The hydrologic response of the basin was simulated based on Hydrologic Modeling System developed by the Hydrologic Engineering Center (HEC-HMS). Weather Generator version 6 from the Long Ashton Research Station (LARS-WG 6.0) was utilized to forecast climate data from 2021 to 2080. These forecasted climate data were then assigned as weather inputs to HEC-HMS to downscale the climate predictions of five large-scale general circulation models (GCMs) for three possible emission scenarios (such as RCP 2.6, RCP 4.5, and RCP 8.5). The alteration of the Kalloni hydrologic regime is evaluated by comparing GCMs based estimates of future streamflow and evapotranspiration with business as usual (BaU) scenario. Variation was noted in seasonal and in annual scale forecasting of long-term average discharges, which show increasing trend in autumn and decreasing in summer and there is observed a general upward trend of actual evapotranspiration losses.

Assessing the hydrologic regime alteration of a Wadi system as a proxy on initial ecological responses to climate change and growing water demand

<p>Most Wadi systems of the world are threatened by climate change and unsustainable consumption through different water use systems (WUS) which can result in an alteration of the hydrologic regime, a deterioration of water resources, and their valuable ecosystems. The objective of this study is to assess the impact of climate change and growing water demand on the alteration of the Halilrood River’s flow regime and the associated impacts on the ecosystem of the Jazmorian wetland in central Iran. The Soil and Water Assessment Tool (SWAT) model is used to simulate the flow regime of the near and far future (2030-2059 and 2070-2099). Based on 32 Indicators of Hydrologic Alteration (IHA) in conjunction with the Range of Variability Approach (RVA) alterations in the flow regime are evaluated. Impacts of three scenarios for future water use (No-, Constant-, and Projected-WUS) are assessed. No-WUS assumes pristine conditions in the future when no water use system are included in the model (no demand) and we only account for the impact of climate change; Constant-WUS assumes unaltered groundwater demand in the future; and Projected-WUS corresponds to the increases in the number of water use systems in the future (increasing demand). Flow regime alteration assessment indicates that climate change will severely affect the magnitude of monthly and annual extreme flows, frequency and duration of high and low Pulses in the Halilrood Basin, especially in the far future. The comparison of model simulations under different scenarios shows that the impact of climate change was more intense when growing water demand in the future is taken into account. The result of the RVA test indicates moderate and high level of changes for 18 indicators, thus likely affecting the environmental flows required for the health of the downstream wetland.</p>

Sustainable use of water resources in a Wadi system facing climate change impacts and growing groundwater demand

Understanding current and possible future alterations of water resources under climate change and increased water withdrawal allows for better water and environmental management decisions in arid regions. This study aims at analyzing the impact of groundwater withdrawals and climate change on groundwater sustainability and hydrologic regime alterations in a Wadi system in central Iran. A hydrologic model is used to assess streamflow and groundwater recharge of the Halilrood Basin on a daily time step under different scenarios over a model setup period (1979–2009) and for two future scenario periods (near future: 2030–2059 and far future: 2070–2099). The Indicators of Hydrologic Alteration (IHA) with a set of 32 parameters are used in conjunction with the Range of Variability Approach (RVA) to evaluate hydrologic regime change in the river. The results show that groundwater recharge is expected to decrease, and is not able to fulfil the increasing water demand in the far future scenario. The Halilrood River will undergo low and moderate flow alteration under both stressors during the near future as RVA alteration is classified as high for only three indicators, while in the far future, 11 indicators lie in high range. Absolute changes in hydrologic indicators are stronger when both climate change and withdrawals are considered in the far future simulations, since 27 indicators show significant changes and RVA show high and moderate level of changes for 18 indicators. Considering the evaluated RVA changes, future impacts on the freshwater ecosystems in the Halilrood Basin will be severe. The developed approach can be transferred to other Wadi regions for a spatially-distributed assessment of water resources sustainability.

Uncertainties and risks in reservoir operations under changing hydroclimatic conditions

Uncertainties and risks associated with hydroclimatic variations pose a challenge to the management and planning of water resources systems. This study demonstrates the importance of understanding the changing hydrologic regime of the Feather River Basin (FRB) and its impacts on water resources decision variables (i.e., storage requirement and performance of a water supply reservoir). A simple storage–yield–reliability model (S–Y–R) is used to quantify the risk of the stationary-based designed reservoir under the temporal variation and nonstationarity in N-year blocks of the Feather River Inflow into Lake Oroville (FRI). Furthermore, the potential linkages of the long-term variability in the FRI to climate variations are investigated by applying wavelet spectrum and coherence analysis to the FRI and atmospheric–oceanic indices (e.g., ENSO and PDO). The results show substantial variations in the FRB hydrologic regime over different timescales with episodes of abrupt shifts toward significantly higher storage requirements, and decrease in the reservoir performance during historical periods of high FRI variance and lag-1 serial correlation. Although the mean inflows are high, the storage capacity is increased by (a) 38 and 48% due to the 5 and 20% increase in the FRI variance during the periods 1904–1953 and 1960–2009, respectively, and (b) 34% due to the increase in the serial correlation coefficient in the period of 1750–1799. Likewise, reservoir performance significantly decreased for the same reasons in the same critical periods. The reliability and resilience dropped to 74 and 29% (1904–1953) and to 76 and 50% (1960–2009 period) due to the increased variance of FRI, while vulnerability reached 70% during the high lag-1 correlations in 1532–1581 and 1564–1613, and 40% in 1904–1953 due to the high FRI variance. Furthermore, the wavelet coherence analysis observes strong associations between the streamflow and climate teleconnection patterns in specific periodic cycles during the same critical periods which link the variability in FRI and decision variables to the hydroclimatic variations. These linkages give a primary indication for the reservoir storage requirement characterization.

Morphometric characteristics and hydrological dynamics in micro-basins with different land uses of cerrado soils in Mato Grosso

Understanding the hydrologic regime, and monitoring runoff at the micro-basin scale is critical for understanding water availability, and for managing water resources in strategic biomes such as the cerrado. The objective of this research is to evaluate morphometric characteristics and the hydrologic regime and determine their relationships with soil characteristics and typical land-use in the cerrado biome. To reach this objective morphometric characterization, runoff and precipitation monitoring, and determination of the water retention curve were conducted in three micro-basins in the municipality of Campo Verde, Mato Grosso. These micro-basins each have a different, but regionally typical land-use and were selected strategically to represent this area of cerrado: agriculture, pasture and native vegetation. The results obtained allow for the analysis of the hydrologic regime throughout the period measured. Micro-basins with native vegetation and pasture, with greater altimetric range and more sandy soils, show greater erosion. Despite this, the micro-basin with pasture cover showed greater regulation of runoff. The micro-basin with agriculture showed less regularization of water flux due to the physical characteristics of the local soils.