Springer Science and Business Media LLC

Lake Qinghai, the largest saline lake with an area of 4,260 km2 (2000) and average depth of 21 m (1985) in West China, has experienced severe decline in water level in recent decades. This study aimed to investigate water balance of the lake and identify the causes for the decline in lake level. There was a 3.35-m decline in water level with an average decreasing rate of 8.0 cm year−1 between 1959 and 2000. The lake water balance showed that mean annual precipitation between 1959 and 2000 over the lake was 357 ± 10 mm, evaporation was 924 ± 10 mm, surface runoff water inflow was 348 ± 21 mm, groundwater inflow was 138 mm ± 9 and the change in lake level was −80 ± 31 mm. The variation of lake level was highly positively correlated to surface runoff and precipitation and negatively to evaporation, the correlation coefficients were 0.89, 0.81 and −0.66, respectively. Water consumption by human activities accounts for 1% of the evaporation loss of the lake, implying that water consumption by human activities has little effect on lake level decline. Most dramatic decline in lake level occurred in the warm and dry years, and moderate decline in the cold and dry years, and relatively slight decline in the warm and wet years, therefore, the trend of cold/warm and dry climate in recent decades may be the main reasons for the decline in lake level.

Estimation of lake hydrologic budgets is essential for sustainable water management due to increasing water demand and uncertainties related to climate change. The updated turbulent diffusion transfer algorithms were developed and incorporated in the DLM-WQ model developed at UC Davis to estimate the Upper Klamath Lake’s dynamics, and heat and hydrologic budget. The exchange coefficients for latent heat (CEN), sensible heat (CHN), and wind drag (CD) of the turbulent diffusion model were calibrated using coefficient of correlation as the objective function. The agreement between estimated and measured lake water elevation and temperature are found to be excellent with correlation coefficients 0.99 and 0.95, respectively. The heat and hydrologic budgets are more sensitive to evaporative heat loss (35 %) than sensible heat exchanges (11 %). The stream inflow and lake outflow dominate the hydrologic budget with approximately 47 % due to stream inflow and approximately 44 % due to lake outflow. Precipitation directly on the lake and evaporation from the lake are only 3 % and 6 %, respectively. The lake mixes to the bottom sporadically during spring and summer. Estimated deep mixing for the period 1994–1996 shows the lake’s increasing stability without a deep mixing event for approximately 4 months during summer in 1996. Prolonged stratification in the hypereutrophic lake is expected to lead to hypoxia near the sediment surface resulting in exacerbation of existing ecological problems. The DLM-WQ model can be applied to a broad range of lakes/reservoirs with selection of appropriate CEN and CHN value for lake/reservoir dynamics and water resources planning evaluation.

The latitude and layout of the Betic orography make southeastern Spain one of the driest climatic regions in Europe. Most of its territory is part of the Segura Hydrographic Demarcation (DHS). The DHS features a water resources vs water demands deficit equal to 480 hm3/year (1 hm3 = 100 m3) during the 2009–2015 hydrologic planning period. A new paradigm for water policy in Spain has emerged for the hydrological planning period (2016–2021), which calls for a greater contribution of unconventional resources (desalination and reuse of municipal sewage). The investment made in the DHS, in terms of sewage purification and regeneration, produces about 110 hm3/year of purified sewage annually. Irrigation is the main consumer of these reuse flows. Irrigation districts develop conveyance and storage infrastructure to import treated sewage from Sewage Treatment Plants (STPs) and Water Regeneration Stations (WRSs). Anthropogenically-caused climate change has brought additional stress on surface water and groundwater, thus making water recycling an important component of the water supply portofolio in Spanish arid regions. Recycled water increases the resources of semi-arid regions (up to 10% of total resources), like in the Southeast of Spain. It is of great social value as it contributes to water safety, economic dynamism and biodiversity. Investment made in this sector and public policies make possible the implementation of recycling system, turning this limited resource into a social, political and economic interest, reaching levels of 99.5% purified and 97% reused in Murcia. Similar regions could import this management system and the concessionary model of reclaimed water. In dry regions, these water management models make recycled water, rather than an alternative, a significant complement to local water resources.

An entropy-based approach is developed for assessing natural groundwater recharge in unconfined aquifers from Southern India. The wells are located in weathered zones which exhibit spatial variability in natural recharge. To determine the fractional amount of rainfall (called natural recharge) marginal entropies and transinformation of rainfall and depth to the water table at selected wells are calculated. Then a ratio of transinformation to marginal entropy of rainfall is used as a measure for assessing natural recharge. Calculated natural recharge yields a good agreement with the results of recharge zones obtained using Remote Sensing (RS) and Geographical Information System (GIS) techniques.

Recently many runoff models based on cellular automaton (CA) have been developed to simulate floods; however, the existing models cannot be readily applied to complex urban environments. This study proposes a novel rainfall-runoff model based on CA (RRCA) to simulate inundation. Its main contributions include a fine runoff generation process that considers 12 urban scenarios rather than a single land use type and the confluence process determined by the new transition rules considering water supply and demand (WS-WD transition rules). RRCA was compared with another CA based flood model (E2DCA). With the benchmark model, the results showed that there was good agreement, with an R-squared greater than 0.9, and that RRCA was more sensitive to waterlogging levels than E2DCA. Furthermore, the simulated vegetation interception, infiltration and drainage processes had varying degrees of impact on waterlogging. Corresponding measures can be taken in urban flood management according to the identification of areas experiencing drainage difficulties.

Floods are one of the most destructive natural disasters which compensation of their effects inflicts immense costs especially in areas with human developments such as cities. Moreover, supplying water for demands particularly during the drought period is a challenging issue in water resource planning. The aim of this study is to propose a model for optimal operation of a reservoir with enhancing downstream demands supply and flood damage mitigation objectives. The model is developed by coupling MODSIM, river network simulation DSS with the imperialist competitive optimization algorithm (ICA). Gotvand Dam in southwestern Iran is the case of study and amounts of water storage in the reservoir in daily time-steps are the decision variable. Results indicate efficiency of the proposed optimization-simulation approach, suggesting that flood damages can be controlled with proper planning while ensuring that downstream water demands are satisfied. As an instance of results, the optimum reservoir rule curve obtained by the proposed model is able to manage a flood entering to the reservoir 11 times greater than the safe flow in the downstream reach and release it lower than the safe flow rate.

Hydrodynamic river models are applied to design and evaluate measures for purposes such as safety against flooding. The modelling of river processes involves numerous uncertainties, resulting in uncertain model outcomes. Knowledge of the type and magnitude of uncertainties is crucial for a meaningful interpretation of the model results and the usefulness of results in decision making processes. The aim of this study is to identify the sources of uncertainty that contribute most to the uncertainties in the model outcomes and quantify their contribution to the uncertainty in the model outcomes. Experts have been selected based on an objective Pedigree analysis. The selected experts are asked to quantify the most important uncertainties for two situations: (1) the computation of design water levels and (2) the computation of the hydraulic effect of a change in the river bed. For the computation of the design water level, the uncertainties are dominated by the sources that do not change between the calibration and the prediction. The experts state that the upstream discharge and the empirical roughness equation for the main channel have the largest influence on the uncertainty in the modeled water levels. For effect studies, the floodplain bathymetry, weir formulation and discretization of floodplain topography contribute most to the uncertainties in model outcomes. Finally, the contribution of the uncertainties to the model outcomes show that the uncertainties have a significant effect on the predicted water levels, especially under design conditions.

Groundwater studies in several African countries show that the contamination of water-supply aquifers is mainly due to improper placement of land-based activities such as agriculture, industries, waste disposal. In South Africa, groundwater pollution is also of increasing concern due to fast population growth and accompanying development. Groundwater protection zoning is a supplemental methodology for groundwater management that incorporates land use planning. The land is managed to minimize the potential of groundwater contamination by human activities that occur on or below the land surface. The various benefits associated with implementation of protection zoning are discussed for stakeholders such as communities, water supply companies, ecosystems and policy makers. A South African case study is presented comparing the cost of protection with the cost incurred due to the treatment of sick and dying people due to contaminated drinking water. These benefits must be communicated to the stakeholders to start the implementation at all management levels. Implementation steps of groundwater protection zones are discussed and can be tested even with low budgets and little data available. Monitoring and reassessment of protection zones are important to test the effectiveness and prove to decision makers that the money was well spent. The legal framework for implementation of groundwater protection zoning in a South African context is described, where the water law makes provision for tools like differentiated protection, licensing and recovery of cost. Challenges regarding implementation of groundwater protection are discussed with some action steps on how to move forward.