Pond Water Level Research Articles

Thermal regime of High Arctic tundra ponds, Nanuit Itillinga (Polar Bear Pass), Nunavut, Canada

Abstract. This study evaluates the seasonal and inter-seasonal temperature regime of small tundra ponds ubiquitous to an extensive, low-gradient wetland in the Canadian High Arctic. Pond temperatures can modify evaporation and ground thaw rates, impact losses of greenhouse gases, and control the timing and emergence of insects and larvae critical for migratory-bird feeding habits. We focus our study on thaw ponds with a range of hydrologic linkages and sizes across Nanuit Itillinga, formerly known as Polar Bear Pass (PBP), Bathurst Island, and compare their thermal signals to other Arctic ponds. Pond temperatures and water levels were evaluated using temperature and water level loggers and verified by regular manual measurements. Other environmental data collected included microclimate, frost table depths, and water conductivity. Our results show that there is much variability in pond thermal regimes over seasons, years, and space. Cumulative relative pond temperatures were similar across years, with ponds normally reaching 10–15 °C for short to longer periods, except in 2013, which experienced a cold summer season during which pond temperatures never exceeded 5 °C. Pond frost tables and water conductivities respond to variable substrate conditions and pond thermal patterns. This study contributes to the ongoing discussion on climate warming and its impact on Arctic landscapes.

Mitigation measures of storm surge inundation at an onshore aquaculture farm

Onshore pond-based aquaculture occupies a large proportion of coastal fisheries and is vulnerable to marine flooding. One common adaptation strategy is constructing sluices along inlets to prevent flooding. The efficacies of sluices typically depend on gate operation, associated risks, and flooding processes. However, few studies were focused on inundation characteristics and mitigation measures for valuable aquaculture farms. To assess the effectiveness of sluices in flood mitigation, we simulated storm surge inundation processes in a coastal aquaculture farm in the Pearl River Delta, where storm surges frequently occurred. The newly constructed sluice can substantially reduce the extent and severity of flood inundation. The antecedent water levels in fish ponds significantly affected the inundation processes, and a water level of −0.5 ∼ 0 m below mean sea level was a recommended value for reducing inundation risk. Our modeling results regarding the effect of the sluice and antecedent water levels on mitigating flood inundation will provide a reference for flood control of onshore aquaculture farms.

Sistem Kontrol Kadar Amonia Dan Tinggi Air Pada Kolam Penangkaran Tukik Penyu

Turtles are also one of the animals whose population is decreasing day by daydue to several factors ranging from climate change, disease, environmentaldamage and inadequate processing of conservation techniques and so on. Withthe status of turtles being endangered, special attention is needed for turtles inthe form of cultivating turtles, especially when the turtles are still 0-2 years oldor known as hatchlings. One of the important indicators in hatchling cultivationrequires good seawater quality management. One of the parameters of goodseawater quality is ammonia levels. This ammonia level can be formed naturallyby metabolic wastes and also food waste that decomposes in the water whichresults in the formation of ammonia levels. In turtle hatchling ponds it is alsonecessary to adjust the water level in the pond with a height of 5cm - 10cmbecause newborn hatchlings cannot dive. The importance of regular waterquality control such as ammonia levels and water level in ponds is veryimportant for the success of hatchling cultivation. Therefore, a research onmonitoring and controlling systems for ammonia levels and water levels usingthe TCS3200 color sensor is carried out to read the change in water color afteradministration of an ammonia test solution which will show the value ofammonia levels in water. Previously, water sampling was carried out by DCpumps and ultrasonic sensors to detect water level. Where this system canmonitor and control ammonia levels and height automatically and the resultscan be viewed using a smartphone through the Blynk application

An automatic waste cleaning system in shrimp ponds with digital image processing using the internet of things

Super intensive shrimp pond wastewater with a stocking density of 750-1,250 individuals/m2 contains an average total suspended solids (TSS) of 798-924 mg/L, dissolved organic matter (BOT) of 81,227-88,641 mg/L; total nitrogen (TN) 9.8389-14.4260 mg/L; and total phosphate (TP) 7.8770-11.8720 mg/L. This value has exceeded the threshold limit of the permissible pond wastewater standard so it has the potential to hurt the environmental quality of water bodies receiving the waste load. making a more intensive vannamei shrimp farming pond cleaning system using turbidity sensors to read turbidity in shrimp farming ponds and ultrasonic sensors as readers of the water level in shrimp farming ponds and using a camera to detect the presence of foam waste in shrimp farming ponds and the Raspberry Pi microcontroller as a center system control on control devices and monitoring of all sensors then the output data will activate the drainage of leftover shrimp feed and shrimp waste from drainage to disposal using PVC pipes and automatic faucets that are driven using DC power window motors. The Internet of Things (IoT) automatic system in the construction of a waste cleaning device for shrimp ponds was built using a turbidity sensor that can detect the level of turbidity in water with an accuracy of 0.51%. The need for additional water in the pond is assisted by an ultrasonic sensor which provides information to the water pump with an average accuracy of 0.56%. To detect foam waste using a webcam camera as a foam detector.

Monitoring the spatial distribution of water quality of an urban stormwater pond using satellite images

Stormwater ponds play a critical role in managing urban runoff and mitigating the impact of pollutants on receiving water bodies. This study investigates the potential of remote sensing (RS) techniques in retrieving water level and key water quality parameters in urban stormwater wet ponds. Specifically, the focus is on water level, chlorophyll-a (Chl-a), total suspended solids (TSS), turbidity, and Secchi depth (SD). The results indicate that RS techniques can provide reliable estimates of water level, Chl-a, turbidity, SD, and TSS in urban stormwater wet ponds. Results revealed that Chl-a concentrations are higher near the inlets and within the forebay, with a significant decrease downstream of the forebay. TSS and total dissolved solids (TDS) concentrations follow a similar pattern to Chl-a, being higher near the inlet and within the forebay, but significantly lower downstream. Notably, the highest concentrations of TSS, TDS, and Chl-a are observed in July, likely due to heavy rainfall events during that period. Through principal component analysis (PCA) and correlation analysis, the study effectively captured the interrelationships among the water quality parameters in the stormwater pond. The spatial distribution of TSS and Chl-a shows a correlation. Furthermore, the study uncovers a relationship between water temperature and Chl-a concentration, with Chl-a decreasing as the temperature exceeds 20 °C and increasing when it drops below 20 °C. This relationship is influenced by sunlight availability, which affects Chl-a growth, as evidenced by variations in Chl-a concentration between the water column's bottom layers and surface. Overall, this research highlights the potential of utilizing RS techniques to retrieve water quality parameters, providing valuable information for water managers and decision-makers. The ability to generate maps of these parameters using reflected light measurements above stormwater wet ponds also contributes to effective water quality management strategies.

THE CURRENT STATUS OF TECHNICAL AND FINANCIAL ASPECTS IN SQUARE-HEAD CLIMBING PERCH (Anabas Testudineus) CULTURED IN HAU GIANG PROVINCE, VIETNAM

The study was conducted to assess the current status of technical and financial aspects to contribute to proposing solutions and to overcome the development directions for the square-head climbing perch culture next time. The study was carried out in Hau Giang Province from February to May 2020 through interviewswith 44 farmer households in a well-designed form. The results showed that the average yield is 11.5±4.43 tons/1,000 m2/crop, the average profit is 16.4±23.5 million VND/1,000 m2/crop, the high total production cost is 283.1±114.9 VND/1,000 m2/crop, in which the food cost is the highest with 84.6%. The benefit ratio was0.06 times and there are 64% of net profit and 38% of net loss farmers. The factor of survival rate, fingerling size, density stocking, experience, price, FCR and pond water level impacted yield and profit. Besides the advantages of natural conditions and self–supply fingerling, the squarehead climbing perch system currently faces many difficulties, such as capital shortage, product output depending on traders’ price, product standards, and harvest time.

The impacts of water level fluctuations from paddy fields and aquaculture ponds on wetland habitats for wintering waterbirds: Implications for wetland management

The distribution and composition of wetland habitats for wintering waterbirds are heavily influenced by water level fluctuations. Through polder construction and aquaculture activities, paddy fields and aquaculture ponds have decreased the lateral connectivity of water level fluctuations in the lake. However, the impacts of water level fluctuations on habitat suitability, which can be seen using high-resolution images analysis, often cannot separate disturbances caused by the paddy fields and aquaculture ponds, and it is difficult to capture the actual impact of water level fluctuations on wetland habitats. Based on remote sensing image data and hydrological data, we selected Caizi Lake as a study site and comparatively analyzed the changes in wintering waterbird habitats in a water level sequence under the two scenarios. Our work showed that paddy fields and aquaculture ponds should be considered as potential options for creating more suitable habitats for migratory waterbirds if combined with reasonable and effective management of the water level within the paddy fields and aquaculture ponds. The present study results could facilitate the management and sustainable utilization of Caizi Lake wetlands and provide support for creating small habitats by managing the water levels of paddy fields and aquaculture ponds.

Modifikasi Prototipe Robot Pelontar Pakan Ikan dan Sistem Monitoring Level Air pada Tambak

Fisheries are one of the sectors that are relied upon for national development. In 2019, the export value of Indonesian fishery products reached Rp. 73,681,883,000, which is an increase of 10.1% from 2018 exports. Marine products such as shrimp, tuna, squid, octopus, crabs and seaweed are sought-after commodities. The development of fish farming can be carried out if the availability of good quality seeds and available in sufficient quantities, proper feed, prevention and treatment of disease and a good living environment. The survival rate at the seed stage is influenced by the type of feed given and the amount according to the needs of the fish. This study aims to modify the previous feed throwing robot so that it can be thrown further and the feed is not destroyed so that it can help the work of fish pond farmers in providing fish feed, modify the tool to help fish pond farmers work in knowing the pond water level, design and build a filling system. manually and automatically using solar panels and modifying the information system on the previous tool so that it can display more information to fish pond farmers. The results showed that the ideal distance of feed throw 5.1 meters, and maximum charging using solar panels 14.28 Watts per hour. The feeding system, water level regulator, information system and charging system can facilitate the pond management process

Comparative reproductive parameters of sympatric Lesser Scaup (<i>Aythya affinis</i>) and Ring-necked Duck (<i>Aythya collaris</i>) in parkland Manitoba

Waterfowl managers are concerned that Lesser Scaup (Aythya affinis) breeding populations remain below conservation goals. Contrasting population growth trajectories for sympatric, phylogenetically similar Lesser Scaup and Ring-necked Duck (Aythya collaris) at Erickson, Manitoba, Canada, prompted investigations that might help explain these trends and provide insight for population management of both species. We collected data (2008–2018) on productivity (broods/pair), water levels, hatching dates, age class-specific brood sizes, duckling daily survival rate, and brood female response to disturbance and compared results between species over time. Ring-necked Duck productivity was greater (0.42 versus 0.28, P < 0.01), hatching dates were earlier (19 July versus 27 July, P < 0.001), and females attempted to hide their broods more often than did Lesser Scaup (16% versus 3%, P < 0.001), but Ring-necked Duck age class-specific brood sizes were smaller than for Lesser Scaup (Ia broods: 6.1 versus 6.8, P = 0.02; IIa broods: 5.6 versus 6.2, P = 0.02). Duckling daily survival rates were similar. Productivity of both species was positively related to annual change in pond water level and both demonstrated similar rates of response to change. There was no support for an association between productivity and one- or two-year lagged pond water levels. Consistent with previous findings, our results suggest that greater Ring-necked Duck productivity is a likely proximate cause for the differing population growth trajectories between the species. We suggest that better Ring-necked Duck nest placement may be a contributing factor to the greater nest success observed.

Grow-out of mud crab crablets, Scylla paramamosain in brackishwater pond with different feeding strategy

This research aimed to know the crablet growth and survival rate after cultured in brackishwater pond with different feeding strategy. Nine ponds fenced by black plastic net, each size of 100 m2 and pond water level at 60-80 cm. Crablets (weight size of 1.51+0,15 g/ind) from hatchery stocked at the density of 1 ind./ m2. Chopped trash fish at biomas 3-5% was given to the crablets as feed at every day (A), at every two days (B) and at every three days (C). Each treatment in three replications. At the three months of culture the highest final weight (128.23+21.19 g/ind.) in treatment A, then treatment C (107.04+25.24 g/ind.) and treatment B (95.60+5.79 g/ind.). Treatment A with the highest daily growth rate (1.41+0.1 g/day) and significantly different (P<0.05) with the daily growth rate in treatment B (1.04 +0.06 g/day) and treatment C (1.17+0.09 g/day). The highest survival rate (39.7%) after four months cultured was obtained in treatment B. High salinity attained to 54 ppt in the end of third month of culture was caused the high numbers of mud crab mortality in all treatments.

Fluctuating pond water levels and aquatic insect persistence in a drought-prone Mediterranean-type climate

In dry areas, natural and artificial ponds experience frequent water level fluctuation, affecting conditions for some aquatic and amphibiotic taxa. Water beetles, bugs, and dragonflies make up much of pond diversity, and are responsive to changes in environmental conditions. Using a drought-prone pondscape within the Greater Cape Floristic Region biodiversity hotspot, we determine (1) the relative extent to which species richness, abundance, and composition are affected by pond water level fluctuation, (2) the effects of environmental variables and vegetation characteristics relative to fluctuating water levels, and (3) make recommendations to improve pondscape conservation. We found that the degree of fluctuation had a significant effect on beetle species richness, but had no significant effect on the other focal taxa. Water temperature, pH, and conductivity, and vegetation cover and composition were drivers of aquatic insect species richness, abundances, and assemblage structures. Habitat heterogeneity supported rich aquatic insect assemblages. We recommend that a range of ponds with various degrees of water level fluctuation should be maintained, along with naturally diverse marginal vegetation. Such a dynamic pondscape can contribute greatly towards maintenance of local and regional aquatic insect diversity in drought-prone regions and should be considered as a main focus in conservation efforts.

ДВУХПРУДОВОЙ НАГУЛЬНО-ВЫРОСТНОЙ РЫБОВОДНЫЙ КОМПЛЕКС

Purpose: development and description of the layout and design solution for a two-pond feeding nursery fish-breeding complex, which characterizes by compact placement of its constituent structures and their adaptation to the topographic conditions of the territory. Materials and methods. The theoretical and empirical basis for the development was made up of well-known recommendations on design and construction of pond complexes and survey data of operating fish-breeding facilities and their structures. During the development, the technologies of search design of engineering projects in compliance with fish breeding requirements and restrictions were used. Results. The fish-breeding complex includes: two fish-breeding ponds with a common dividing dam and a water supply system including a pumping station; water supply pipe system; a system of devices and structures that ensure the release of fish grown in ponds into a fish trap; spillway devices for discharging water from ponds and a fish trap with a set of regulating elements. Fish ponds are located on the floodplain lands of the river Don and are formed by protecting dikes. The bed of the reservoirs is planned with sections with longitudinal and transverse slopes to the water-fish collecting and-transporting ditches arranged in their bottom, allowing them to be emptied and the fish grown in the ponds to be directed to the outlet structures. The release of fish from the ponds is carried out by two tower water outlets. The design of the fish trap provides for the accumulation and seine fishing, it is equipped with means for regulating water discharge and maintaining conditions for fish. Conclusions. The developed layout and design solution for a two-pond fish-breeding complex with one fish trap is adapted to the local relief and the difference in water levels in ponds and in water intake. The implemented layout and design solutions can be used in the development of similar objects

Reconstructing the groundwater recharge history for the Plymouth-Carver Aquifer Massachusetts, USA

Groundwater systems can respond to climate forcing and millennial climate shifts more slowly than other components of the hydrologic cycle, making it difficult to reconstruct the influences and responses of groundwater to changing climate. Here, we test the linkage between climate change and groundwater responses by using water level changes situated in areas with permeable, unconfined aquifers systems. For hydroclimate histories, we compare moisture models from terrestrial water level reconstructions with predictions of available water from a transient earth system climate model. We focus our analysis on several small waterbodies with Holocene-era proxy measurements that are connected to the Plymouth-Carver glacial aquifer in southeastern Massachusetts, USA. Using these pond- and marsh-based records, we reconstruct groundwater recharge histories along individual groundwater flow paths using water level and sea level reconstructions with an analytical solution to the groundwater flow equation. We find that the water level reconstructions could contain both hydroclimate and sea level signals, with the early Holocene water levels primarily due to hydroclimate with predominantly a sea level signal after ∼7.5 ka cal BP. Our results indicate that sea level influenced coastal pond water levels, and sea level may play a more significant role than effective moisture over certain periods in the Holocene for terrestrial water bodies hydraulically connected to the evolving position of the coast. Future climate reconstructions developed from water level histories from low-elevation inland water bodies may benefit from examining the potential influence of sea level in addition to hydroclimate, but additional model validation and consideration of other cryosphere and glacial processes are needed to fully resolve sea level as a driver of terrestrial water level change.

Notes on the Predation of Rough-Footed Mud Turtles (Kinosternon hirtipes) in West Texas, USA

Little is known concerning predation of rough-footed mud turtles (Kinosternon hirtipes), a species of conservation concern in Texas, USA. During field studies conducted from 2007 to 2016, we documented 8 instances (1 juvenile, 2 males, and 5 females) of predation among individuals of one of the few (<10) remaining populations of K. hirtipes in Texas. Predation was attributed to raccoons (Procyon lotor; n = 5) and feral pigs (Sus scrofa; n = 2); the predator responsible for the death of one of the turtles could not be determined. Turtles are vulnerable to predation when exposed by low water levels in ponds, when making overland movements between ponds, and during nesting forays ashore. To reduce the likelihood of predation, we recommend maintaining adequate water levels in wetlands, linking wetlands with ditches, encouraging the growth of aquatic vegetation, and providing experimental raccoon-proof nest mounds.

Pond and Irrigation Model (PIM): a Tool for Simultaneously Evaluating Pond Water Availability and Crop Irrigation Demand

Agricultural ponds are an important alternative source of water for crop irrigation to conserve surface and ground water resources. In recent years more such ponds have been constructed in Mississippi and around the world. There is currently, however, a lack of a tool to simultaneously estimate crop irrigation demand and pond water availability. In this study, a Pond-Irrigation Model (PIM) was developed to meet this need using STELLA (Structural Thinking, Experiential Learning Laboratory with Animation) software. PIM simulated crop land and agricultural pond hydrological processes such as surface runoff, soil drainage, and evapotranspiration as well as crop irrigation demand and pond water availability. More importantly, PIM was able to decide when to conduct crop irrigation based on management allowable depletion (MAD) root zone soil water content and to determine optimal ratios of agricultural pond size to crop land with sufficient pond water available for crop irrigation. As a case demonstration, the model was applied to concomitantly estimate row crops (i.e., corn, cotton, and soybeans) water irrigation demand and pond water availability in a farm located at East-central Mississippi. Simulations revealed that corn used more soil water for growth than soybeans, whereas soybeans needed more irrigation water than corn and occurred due to less rainwater available for soybeans growth. We also found that there was one time for corn, zero time for cotton, and two times for soybeans when the pond water level was drawn to near zero for irrigation from 2005 to 2014. PIM developed in this study is a useful tool for estimating crop irrigation demand and pond water availability simultaneously.

Interactions of physico chemical parameters with bacterial populations in earthen and lined white legged shrimp (Penaeus vannamei) culture ponds

Bacterial population involved in nutrient recycling in two white legged shrimp Penaeus vannamei culture systems viz., earthen and lined ponds was studied to understand the influence of physico-chemical parameters of pond water. Among the parameters studied, pH found to be influencing physico-chemical parameters and microbial profile in lined or earthen pond. Significantly negative correlation (P<0.01) was observed between pond water pH and carbonates, nitrate-N, total ammonical nitrogen (TAN), available phosphorus (P) and available potassium (K) content of sediment. Similarly significantly negative correlation (P<0.01) was observed with total bacterial count (TBC), total presumptive vibrio count (TVC), sulphur reducing bacteria (SRB) in earthen ponds. Additionally, significant negative correlation (P<0.01) was also observed with organic carbon (OC) and available Nitrogen (N) of the pond soil. Nitrogen level of pond soil were significantly correlated (P<0.05) with pond sediment TBC, TVC and SRB and pond water Sulphur Oxidizing Bacteria (SOB). Phosphorus level of pond soil showed significantly positive correlation (P<0.01) with TBC, TVC and sediment SRB population. In both the systems, pH did not show any correlations with SOB indicating the ability of SOB to grow under wide variations of pH levels. In lined ponds, significantly positive correlation (P<0.01) was observed between TAN and nitrate as well as between TBC and TVC. It can be concluded from the study that pond water pH and levels of N, P and K in pond bottom soil can be used as a better indicators of environmental quality for estimating the deteriorating pond conditions. In addition, it can be used as management technique for managing the pond health and environmental conditions.

Recycling Tailings Seepage Water for Diogo Heavy Minerals Mine Sustainability (Northern Senegal)

The sandy Quaternary and the deep Maastrichtian aquifers located in the northern coastal zone of Senegal, from the locality of Kayar in the south to Saint-Louis in the north, constitute the main sources of water supply for urban and local needs as well as mining activities. The Quaternary aquifer that provides the water required for the irrigation of local farmlands, hosts a significant heavy mineral sands deposit currently being mined by the Grande Cote Operations (GCO). As a result of variable rainfall and increased water abstraction, this shallow aquifer has recorded a continuous water level decline since 1970, with potential negative effects on both the social and economic development of the region. The mining of heavy minerals (zircon, ilmenite, leucoxene and rutile) at GCO is realised through conventional dredging techniques that require large volumes of water (up to 60,000 m3/d). The water pumped by the dredge to enable the extraction of the heavy minerals, infiltrates into the shallow aquifer, runs-off into the dredge pond or evaporates. The objective of this study is to evaluate a water balance that enables the provision of a permanent water supply to the dredge pond, whilst minimising the risk of flooding of the cropping depressions adjacent to the mine site or drying out of the farming wells. The hydrodynamic model implemented for this purpose was calibrated and tested during the first year of operation. The Root Mean Squared Error (RMSE) obtained for the calibration is approximately 0.52 m. The predictions indicate a requirement for the system to recover part of the tailings infiltration through dewatering boreholes. The quantity of recycled water is estimated at 16,000 m3/d on average. The model simulations show an additional water requirement, extracted from the deep Maastrichtian aquifer, varying between 23,000 and 28,000 m3/d to achieve the optimum pond water level.

Aquifer recharge with treated municipal wastewater: long-term experience at San Luis Río Colorado, Sonora

This paper presents 10 years of experience in recharging reclaimed waters via infiltration basins in order to reverse overdraft in a previously overexploited aquifer. First, the feasibility of artificial recharge was evaluated using an infiltration experiment to estimate the percolation rates and the capacity for reclaimed water treatment by passing groundwater and treated wastewater through the soil vadose zone to the aquifer in a pilot pond. Ongoing physicochemical and bacteriological monitoring of the reclaimed and recharged water introduced to the aquifer was then conducted to ensure that the native groundwater was not contaminated. After transit through a 20-m-thick vadose zone, the concentration of chloride, manganese and iron increased due to evaporation and dissolution processes, and total removal of coliforms was observed. We found that low water levels in ponds prevented the transport of fine particles to deep layers of the soil vadose zone and maintained a concentration of total suspended solids (TSS) less than 30 mg/l, thus reducing the volume of particles clogging the soil. The pilot test and maintenance practices described in this work have been followed in the development of managed aquifer recharge projects in other semiarid regions.

Pond Dynamics and Supraglacial-Englacial Connectivity on Debris-Covered Lirung Glacier, Nepal

The hydrological systems of heavily-downwasted debris-covered glaciers differ from clean-ice glaciers due to the hummocky surface and debris mantle of such glaciers, leading to a relatively limited understanding of drainage pathways. Supraglacial ponds represent sinks within the discontinuous supraglacial drainage system, and have been documented to sporadically drain englacially. To assess pond dynamics, pond water level measurements were made on Lirung Glacier during May and October of 2013 and 2014. The four field seasons coincided with aerial, satellite, and terrestrial orthomosaic images and digital elevation models, which provided snapshots of the ponds and their surroundings. We analysed the glacier's closed surface catchments to identify surface drainage pathways and englacial drainage points, and compared this to field observations of surface discahrge. The ponded area was higher in the pre-monsoon than post-monsoon, with individual ponds filling and draining seasonally associated with the surface exposure of englacial conduit segments. We recorded four pond drainage events, all of which occurred gradually (duration of weeks), observed diurnal fluctuations indicative of varying supply and discharge, and we documented instances of interaction between distant ponds. The DEM drainage analysis identified numerous sinks >3m across the glacier surface, few of which exhibited ponds (23%), while the field survey highlighted surface discharge only explicable via englacial routes. Taken together our observations provide evidence for widespread supraglacial-englacial connectivity for meltwater drainage paths. Results suggest that progressive englacial conduit collapse events, themselves likely driven by supraglacial pond drainage, enable the glacier surface to evolve into a configuration following relict englacial conduit systems. Within this system, ponds form in depressions of reduced drainage efficiency and link the supraglacial and englacial drainage networks.

Hydrodynamic numerical modelling of the water level decline in four temporary ponds of the Doñana National Park (SW Spain)

Water level changes have been monitored over 25 years in several temporary ponds located at different distances to a pumping area of a tourist resort fringing the Doñana National Park (SW Spain). The numerical model MIKE SHE was set up to simulate pond water levels and hydroperiod fluctuations. It was calibrated for nine hydrological years and validated for two periods of eight hydrological years each to assess whether the duration of the pond wet phase (hydroperiod) significantly deviated from an expected pattern driven by rainfall and evapotranspiration. The model output indicated a satisfactory performance for all simulations. This approach provided two main conclusions: a) a long-term increasing trend in water losses on the pond water balance which has not been followed by a corresponding decreasing trend in rainfall, and b) these water losses were highest in the pond located at < 1 km to the pumping area and lowest in the pond located at a further distance (5.6 km) and at a lower altitude. Our results suggest that, in the long run, a small groundwater abstraction rate has exerted a high hydrological pressure on the closest pond to the pumping area.