Water management in the Mucille area (NE Italy) through hydrologic balance estimation

<p>After abundant rainfalls, the Mucille area (Ronchi dei Legionari, Northeastern Italy) is subject to frequent flooding. Although this area has always been exposed to such hazard, these inundations become problematic since 2001 as they more frequently affect housing and recreational areas, leading the population to believe that the swallow holes draining the area stopped functioning. The increased frequency of intense rainfall events led the municipal technicians to involve the Department of Mathematics and Geosciences of the University of Trieste to assess the situation. The Mucille karstic depression is fed by a spring area and drained by two swallow holes one of which is permanently active while the other operates only during floods. The Mucille springs represent the westernmost drain of the Classical Karst aquifer. During floods, as in-situ discharge measurements are impossible, only a hydrologic balance model may assess the inflow or outflow discharges. The extension of the flooded areas has been mapped. The obtained flooded surface together with high resolution DEM coverage allows to calculate the volume of surface water. Combined with water table levels recorded in an adjacent piezometer, this volume can be computed over time. Thus, the hydrologic balance (inflow minus outflow) can be estimated. This model has been applied to several flood events among which, two were the most important in terms of flooded areas: one in December 2017 and the other in November 2019. During the event of December 2017, the water level reached 7,5 m a.s.l. and the difference between the inflow and the outflow was 880 l/s. The day following the peak, the discharge difference decreased to 273 l/sand the 5 subsequent days the water balance was close to equilibrium. From the eighth day on, the outflow became predominant resulting in a negative budget between -233 and -78 l/s. The flood event of November 2019 reached the maximum inundated area at a water level of 7,8 m a.s.l. with a difference between the inflow and the outflow of 750 l/s . Two days after the peak a negative balance of -200 l/s was recorded and remained negative for the next 5 days. A period of intermittent precipitations increased again the inflow up to 600 l/s. Following a period of ten days with a negative balance the water level returned to the initial values of 5 m a.s.l. This study provides evidences fundamental for the design of measures to mitigate the risk. It estimates the discharge of the swallow holes, confirming their efficiency. Nonetheless it also emphasises the need to improve their draining capacity, especially considering the unsuspected high outflow of the springs at the onset of the flood.</p>

Determination of potential and actual evapotranspiration in watershed, using mathematical models

In this research, it is analyzed the calculation of real evapotranspiration in hydrographic basins, it is taken as a reference the Aguablanca Creek, located in the municipality of Bochalema, North of Santander-Colombia, where it is evaluated the hydrologic balance of this basin from the determination of detailed calculations of four mathematical models, to later evaluate the hydrologic balance of this basin, with the purpose of being able to make a better administration of these resources, as well as the use of the soil, betting on the development of an ecologically sustainable society with low environmental impact. The values of potential and real evapotranspiration, according to the most optimal model ETP Thorwaite 874 mm/year ETR 43712 mm/year, Cenicafe 712.81 mm/year ETR 612.1 mm/year Turc ETR 884.83 mm/year quota ETR 825 mm/year.

Historical and prehistorical water levels of Mormon Lake, Arizona as a measure of climate change on the southwest Colorado Plateau, USA

Mormon Lake, elevation 2166 m with maximum historic surface area of 31.4 km2, lies in a forested endorheic basin covering 103 km2. It is the largest unaltered freshwater body on the 337,000 km2 Colorado Plateau. Prehistorical (before AD 1878) highstands were ca. 9 and 24 m relative to depocenter datum. These levels likely occurred during four multidecadal episodes of cool, wet conditions between ca. 3.55 and 0.20 ka BP. Maximum historical levels (early 1900s) were up to 7.9 m, whereas modern (post-1941) levels were frequently zero or relatively low. Historical climate records indicate reconstructed lake levels correlate directly with annual precipitation and inversely with temperature. Early highstands were associated with above average precipitation and the lowest temperatures of the 116 yr record. The lake receded after 1941; thereafter, frequent drying and low-water levels resulted from recurrent drought and steadily increasing temperatures. Consequently, a wet episode from the 1970s to the 1990s had precipitation like the early 1900s, but highstands were only ca. 3.8 m. The historical lake-level chronology is consistent with changes of hydrologic balance predicted by climate models, that is, reduced effective precipitation (precipitation minus evaporation). These changes, particularly aridification, apparently began in the 1970s or earlier. Global oceanic and atmospheric climate modulate lake levels and regional hydroclimate.

Understanding coastal wetland conditions and futures by closing their hydrologic balance: the case of the Gialova lagoon, Greece

Coastal wetlands and lagoons are under pressure due to competing demands for freshwater resources and climatic changes, which may increase salinity and cause a loss of ecological functions. These pressures are particularly high in Mediterranean regions with high evaporative demand compared to precipitation. To manage such wetlands and maximize their provision of ecosystem services, their hydrologic balance must be quantified. However, multiple channels, diffuse surface water exchanges, and diverse groundwater pathways complicate the quantification of different water balance components. To overcome this difficulty, we developed a mass balance approach based on coupled water and salt balance equations to estimate currently unknown water exchange fluxes through the Gialova lagoon, southwestern Peloponnese, Greece. Our approach facilitates quantification of both saline and freshwater exchange fluxes, using measured precipitation, water depth and salinity, and estimated evaporation rates over a study period of 2 years (2016–2017). While water exchanges were dominated by evaporation and saline water inputs from the sea during the summer, precipitation and freshwater inputs were more important during the winter. About 40 % and 60 % of the freshwater inputs were from precipitation and lateral freshwater flows, respectively. Approximately 70 % of the outputs was due to evaporation, with the remaining 30 % being water flow from the lagoon to the sea. Under future drier and warmer conditions, salinity in the lagoon is expected to increase, unless freshwater inputs are enhanced by restoring hydrologic connectivity between the lagoon and the surrounding freshwater bodies. This restoration strategy would be fundamental to stabilizing the current wide seasonal fluctuations in salinity and maintain ecosystem functionality but could be challenging to implement due to expected reductions in water availability in the freshwater bodies supporting the lagoon.

Understanding coastal wetland conditions and futures by closing their hydrologic balance: the case of Gialova lagoon, Greece

Coastal wetlands and lagoons are under pressure due to competing demands for freshwater resources and climatic changes, which may increase salinity and cause loss of ecological functions. These pressures are particularly high in Mediterranean regions with high evaporative demand compared to precipitation. To manage such wetlands and maximize their provision of ecosystem services, their hydrologic balance must be quantified. However, multiple channels, diffuse surface water exchanges, and diverse groundwater pathways complicate the quantification of different water balance components. To overcome this difficulty, we developed a mass balance approach based on coupled water and salt balance equations to estimate currently unknown water exchange fluxes through the Gialova lagoon, SW Peloponnese, Greece. Our approach facilitates quantification of both saline and freshwater exchange fluxes, using measured precipitation, water depth and salinity, and estimated evaporation rates over a study period of two years (2016–2017). While water exchanges were dominated by evaporation and saline water inputs from the sea during the summer, precipitation and freshwater inputs were more important during the winter. About 40 % and 60 % of the freshwater inputs were from precipitation and lateral freshwater flows, respectively. Approximately 70 % of the outputs was due to evaporation, with the remaining 30 % being water flow from the lagoon to the sea. Under future drier and warmer conditions, salinity in the lagoon is expected to increase, unless freshwater inputs are enhanced by restoring hydrologic connectivity between the lagoon and the surrounding freshwater bodies. This restoration strategy would be fundamental to stabilize the current wide seasonal fluctuations in salinity and maintain ecosystem functionality, but could be challenging to implement due to expected reductions in water availability in the freshwater bodies supporting the lagoon.

Hydrologic balance, net primary productivity and water use efficiency of the introduced exotic Eucalyptus grandis × Eucalyptus urophylla plantation in south-western China

Aims Land cover changes can disrupt water balance and alter the partitioning of precipitation into surface runoff, evapotranspiration and groundwater recharge. The widely planted Eucalyptus trees in south-western China have the potential to bring about hydrologic impacts. Our research aims to elucidate the hydrologic balance characteristics of the introduced exotic Eucalyptus grandis × Eucalyptus urophylla plantation and to assess whether its high productivity results from high water use efficiency (WUE) or large water consumption. Methods A 400-m2 experimental plot was established in an E. grandis × E. urophylla plantation in south-western China. Water balance components, including stand transpiration (Tr), evapotranspiration (Et) and runoff (R) were obtained as follows: Tr was estimated based on sap flow measurements, Et was estimated as the average of surface transpiration and evaporation weighted by the fractional green vegetation cover using a modeling approach, and R was collected using the installed metal frame. Net primary productivity (NPP) was obtained from allometric equation and annual diameter at breast height (DBH) increment determination. Important Findings Annual Et and Tr were 430 ± 31 and 239 ± 17 mm, respectively. Annual Tr accounts for 56 ± 8% of total evapotranspiration on average. WUE (NPP/Tr) of the E. grandis × E. urophylla was estimated to be 3.3–3.9 mmol·mol−1. Based on the comparative analysis of Tr and WUE, E. grandis × E. urophylla had a high productivity due to its high WUE without exhibiting prodigal water use. Meteorological factors including vapor pressure deficit and global solar radiation (Rs) were key factors regulating Et and Tr in our research site. Annual surface runoff, Et and canopy interception occupied 7%, 27–30% and 16% of total precipitation, while the remaining 46–50% of precipitation was used for sustaining groundwater recharge and altering soil water storage. The higher runoff coefficient (7.1%) indicated the weaker capability of E. grandis × E. urophylla to reserve water resource than natural forests and less disturbed plantations. The planting and protection of understory vegetation may decrease the surface runoff and exert beneficial effects on water conservation capacity of Eucalyptus plantation.