Good Quality Water Resources Research Articles

Cultivo de abobrinha sob estresse salino e aplicação exógena de paclobutrazol

ABSTRACT Salinity is considered an obstacle to the production system that limits the growth and yield of crops around the world. Therefore, it is essential to develop strategies to minimize the effects of salinity and increase yield, especially in the semi-arid region of the Northeast, which has limited water resources of good quality for irrigation. The objective was to evaluate the effects of applying paclobutrazol on zucchini crop under salt stress. The experiment was conducted in a greenhouse, in a randomized block experimental design, in a 2 × 5 factorial scheme, with two salinity levels of irrigation water (0.6 and 4.0 dS m-1) and five concentrations of paclobutrazol - PBZ (0; 2; 4; 6 and 8 g L-1), and with four repetitions. Application of 8 mg L-1 PBZ increases stem diameter in zucchini under irrigation of 4.0 dS m-1. Chlorophyll b and total chlorophyll contents increase with PBZ concentration of 4 mg L-1 and irrigation of 0.6 dS m-1. PBZ concentration of 4 mg L-1 increases the relative water content while reducing electrolyte leakage in zucchini under salinities of 4.0 and 0.6 dS m-1 respectively. Root, stem and leaf dry mass of zucchini increases when plants are irrigated with water of 0.6 dS m-1 and subjected to PBZ concentration of 8 mg L-1. PBZ concentrations do not attenuate the effects of salinity on leaf area, crown volume and diameter, vegetative vigor index, chlorophyll a and carotenoids.

Technological Advances in Winery Wastewater Treatment: A Comprehensive Review

The commercial production of wine is directly linked to the use of large amounts of fresh water coupledwith the generation of copious amounts of wastewater containing significant amounts of organic andinorganic substances. The impact of this waste stream on the environment has required the wine industryto implement certain protocols in wastewater management to comply with respective effluent dischargeregulations as set out by local authorities. Reduced accessibility to good quality water resources in recentyears has forced wineries to consider more efficient wastewater management strategies to improve waterrecovery and re-use, thereby promoting more sustainable wine production and minimizing the impact onstressed water resources. This review presents a comprehensive overview of established and emerging,physicochemical, biological, advanced oxidation and hybrid wastewater treatment technologies specificallyapplicable to the wine producing industry. Herein, winery wastewater composition and treatmenttechniques, environmental implications, knowledge gaps, technological operational challenges, alternativedisposal and recycling options of treated winery wastewater are critically evaluated.

Removal of Oil Content from Oil-Water Emulsions Using Iron Oxide/Bentonite Nano Adsorbents

Water scarcity is a challenge that is faced worldwide to secure sustainable good quality water resources. Produced water, associated with the production of gas and oil, usually comes as oil contaminated water, creating real problems in water resources’ management. Removing oil content from produced water is crucial to meet the discharge limits set by governmental legislation. Nanocomposites have attracted attention as potential adsorbents due to their high ability to remove oil content from produced water. In this work, Iron oxide/Bentonite nanocomposites (Fe3O4/Bent NC) were synthesized using ultrasound-assisted co-precipitation methods and evaluated them for oil removal from emulsified oil solutions. SEM, EDS, TEM, XRD, FTIR and VSM were used to characterize the synthesized nanocomposites, confirming the successful formation of superparamagnetic Fe3O4/Bent NC. In addition, the characterization analysis showed that iron oxide nanoparticles were uniformly distributed over bentonite surface with a particle size of 13.55 nm. Performance analysis of oil removal using synthesized Fe3O4/Bent NC was carried out by assessing the effect of Nano-adsorbent dosage, oil initial concentration, adsorption time, and solution pH using batch experiments. A removal percentage of 67% after 90 minutes using only 0.1 grams at 100 ppm oil concentration was obtained. The experimental data were described by Langmuir isotherm model, which suggests a monolayer adsorption of oil onto synthesized Fe3O4/Bent NC. The kinetics data were best described using pseudo-second-order kinetics model. Overall, this study confirms the applicability of Fe3O4/Bent NC as a feasible adsorbent for oil removal from produced water.

Treated wastewater reuse in micro-irrigation: effect of shear stress on biofilm development kinetics and chemical precipitation

ABSTRACT Treated wastewater in micro-irrigation is a promising approach that could be used to decrease the pressure on good quality water resources. However, the clogging of such systems due to biofilm development and chemical precipitation constitute a constraint with the use of treated wastewater (TWW) and lead to lower irrigation system performance. The objective of this work is to study the development of biofilm and composition of fouling due to TWW under shear stresses of 0.7, 2.2 and 4.4 Pa detected along micro-irrigation systems. For this purpose, a Taylor-Couette reactor (TCR) was specifically calibrated for the cultivation of biofilm. The analysis of fouling composition samples (organic and inorganic) shows that biofilm tends to develop under the highest shear stress value (4.4 Pa). Precipitation of calcium carbonate in the form of calcite was observed in conjunction with biofilm growth using X-ray diffractometry (XRD) and thermogravimetric analysis (TGA). These results can be used to ascertain the origins of chemical and biological clogging of drippers and fouling of pipes related to reclaimed water- irrigation.

Anthropic impacts on Sub-Saharan urban water resources through their pharmaceutical contamination (Yaoundé, Center Region, Cameroon)

Sub-Saharan urban centers have to tackle high population growth, lack of sanitation infrastructures and the need for good quality water resources. To characterize the impacts of anthropization on the water resources of the capital of Cameroon (Yaoundé), a multi-disciplinary approach was used in ten sub-watersheds (peri-urban and urban) of the Méfou watershed. Pharmaceutical residues were used as tracers of surface and groundwater contamination caused by the release of domestic wastewater from pit latrines and landfills. A water use survey was conducted in the vicinity of the sampling sites to better assess water use, treatment and management. Available land use and hydro-geomorphological data completed characterization of the sub-watersheds. The combined data showed that natural features (elevation, slope, and hydrography) and human activities (land use) favor rainfall-runoff events and hence surface water contamination. Pharmaceutical monitoring revealed contamination of both surface and groundwater especially in the urban sub-watersheds. Analgesics/anti-inflammatory drugs and anti-epileptic carbamazepine were the most frequently found compounds (in up to 91% of water samples) with concentrations of acetaminophen reaching 5660 ng/L. In urban sub-watersheds, 50% of the groundwater sites used for drinking water were contaminated by diclofenac (476–518 ng/L), carbamazepine (263–335 ng/L), ibuprofen (141–276 ng/L), sulfamethoxazole (<2–1285 ng/L) and acetaminophen (110–111 ng/L), emphasizing the need for a deeper understanding of the interactions between surface and groundwater. The use of groundwater as drinking water by 68% of the total population surveyed raises concerns about population exposure and potential health risks. This case study highlights the need for strategies to limit contamination of the water resource given the predicted future expansion of Sub-Saharan urban centers.

Levels and Distribution of Pollutants in the Waters of an Aquatic Ecosystem in Northern Mexico.

The availability of good quality water resources is essential to ensure healthy crops and livestock. The objective of this study was to evaluate the level of pollution in Bustillos Lagoon in northern Mexico. Physical-chemical parameters like sodium, chloride, sulfate, electrical conductivity, nitrates, and the pesticide dichlorodiphenyltrichloroethane (DDT) were analyzed to determine the water quality available in the lagoon. Although DDT has been banned in several countries, it is still used for agricultural purposes in Mexico and its presence in this area had not been analyzed previously. Bustillos Lagoon was divided into three zones for the evaluation: (1) industrial; (2) communal lands; and (3) agricultural. The highest concentrations of sodium (2360 mg/L) and SAR (41 meq/L) reported in the industrial zone are values exceeding the United Nations Food and Agricultural Organization (FAO) irrigation water quality guidelines. DDT and its metabolites were detected in all of the 21 sites analyzed, in the agricultural zone ∑DDTs = 2804 ng/mL, this level is much higher than those reported for other water bodies in Mexico and around the world where DDT has been used heavily. The water in the communal zone is the least contaminated, but can only be recommended for irrigation of plants with high stress tolerance and not for crops.

Distribution and Removal of Fluoride Ions in the Drinking Waters in the Algerian South (Ouargla as a Showcase)

In certain countries, the Algerian South in particular, where the scarcity of drinking water resources of good quality has constrained the local populations to consume the underground waters that are rich in fluoride. Fluoride constitutes an essential component for the human body in moderate rates, between 0.5 to 1.5mg/l of the consumed water. Nonetheless the population of the Southern Algeria is characterized by a very particular diet marked by tea and dates consumption that contain fluoride in an unidentified and accurate amount within the absence of a full knowledge of all fluoride sources.The present study aims at evaluating the daily amount of fluoride taken and to determine its distribution in water and the main consumed food, as well as localizing the zones of risk and seeks at the end a short term solution to this matter.This work focuses on the evaluation of the rate of fluoride contained in the diet. The dosage of fluoride of the two main watertables feeding the region of the study shows that the rates exceed by far the standards of the WHO. They are comprised in rates oscillating between 1.23 to 2.01mg/l, as for the main food stuff, tea and dates are respectively (0.86 – 2.10mg/l) and (10.48 – 18.24) mg/kg. Actually four methods of fluoride removal from water have been tested, as for the method using Aluminum sulfate and Lime, they provide good findings compared to the other methods.

Effects of Caspian Sea Water on Sugar Beet Seed Germination

The shortage of good quality water resources is becoming an important issue in arid, semi-arid, and coastal zones. Sugar beet yield declines with an increase in salinity, but its sensitivity to salts varies with the salt composition in water and the plant growth stage. The possible use of Caspian Sea water, which its salinity is well below that of open seas, is desirable for irrigation. The aim of this study was to determine effects of various Caspian Sea water regimes on sugar beet seed germination. A randomized complete block (RCB) design was used with four replications of 15 seeds per pot. Eleven different irrigation treatments of Caspian Sea water ranging from 0% to 100% were applied that each treatment indicates the percent of Caspian Sea water to the mixture with the fresh water. Seed germination percent and the mean time to germination data were obtained for 30 days. Statistical analysis revealed that seed germination was significantly affected by Caspian Sea water, particularly by the salinity levels above the electric conductivity (EC) 13 dSm−1.

Poor quality water utilization for agricultural production: An environmental perspective

Agriculture is the largest water user and consumes over 70% of the abstracted freshwater globally. The continuous increase in global population and simultaneous decrease in good quality water resources emphasize the need of using poor quality irrigation water for agricultural production. However, the injudicious use of poor quality irrigation water for crop production can be detrimental to the environment. Irrigation water quality has been considered as a serious environmental factor for the assessment of sustainable development during the last few decades. This paper highlights the need and advantages and disadvantages of long-term application of poor quality water on the soil and plant health. The overall environmental concerns of the approach are discussed in the paper which could be useful for all the stakeholders.

Detecting and distinguishing moisture- and salinity-induced stress in wheat and maize through in situ spectroradiometry measurements

The shortage of good-quality water resources has become an important issue worldwide. In arid and semi-arid environments, low-quality water such as agricultural drainage water, wastewater and saline ground water has become an important supplement to agricultural supply, but with inevitable consequences for plant health and crop yield. In this study, greenhouse experiments were undertaken to investigate the potential of remote sensing to detect and distinguish moisture- and salinity-induced stress in wheat (Triticum aestivum L.) and maize (Zea mays L.) to facilitate crop management. In situ spectroradiometry measurements were collected from plant canopies under natural and artificial illumination at different growth stages to establish when in the growth cycle the effects of these stressors can be distinguished. The results showed that plant reflectance characteristics were affected by both moisture- and salinity-induced stress. Penalized linear discriminant analysis (PLDA) was used to demonstrate that it is possible to distinguish moisture- and salinity-induced stress effects in maize, but not in wheat.

Saline water irrigation effects on soil salinity distribution and some physiological responses of field grown Chemlali olive

The shortage of water resources of good quality is becoming an issue in arid and semi arid regions. Per consequent, the use of water resources of marginal quality is becoming an important consideration, particularly in arid regions in Tunisia, where large quantities of saline water are used for irrigation. Nevertheless, the use of these waters in irrigated lands requires the control of soil salinity and a comprehensive analysis even beyond the area where water is applied. The aim of this study was to investigate the effects of saline water irrigation on soil salinity distribution and some physiological traits of field-grown adult olive trees (Olea europaea L. cv. Chemlali) under contrasting environmental conditions of the arid region in the south of Tunisia. The plants were subjected, over two growing seasons, to two drip irrigated treatments: fresh water (ECe=1.2dSm−1, FW) and saline water (ECe=7.5dSm−1, SW). Saline water irrigation (SW) has led to a significant increase in soil salinity. Furthermore, these results showed that soil salinity and soil moisture variations are not only dependent on water salinity level but are also controlled by a multitude of factors particularly the soil texture, the distance from the irrigation source and climatic conditions (rainfall pattern, temperature average, …). On the other hand, salt treatment reduced leaf midday water potential (LMWP), relative water content and photosynthetic activity and increased the leaf proline content, and this increase was season-dependent. Indeed, LMWP in SW plants decreased to −3.71MPa. Furthermore, the highest level of proline in SW plants was registered during summer period (2.19μmol/mg Fw). The proline accumulation recorded in stressed plants has allowed them to preserve appropriate leaf water status and photosynthetic activity. More to the point, this olive cultivar seems to be more sensible to soil salinity during the intense growth phase. Such tendencies would help to better manage water resources for irrigation, particularly under actual climatic conditions of water scarcity. For example, in the case of the availability of different water qualities, it would be better to preserve those of high quality for olive irrigation during the intense vegetative growth phase, in coincidence with high salt sensitive period, and those of low quality for irrigation during partial growth and plant rest phases. What’s more, the urgent use of saline water for irrigation should not be applied without taking into consideration the different surroundings conditions where it is used, particularly the water salinity level, the soil type, the adopted irrigation system, the degree of the crop salt tolerance, the plant growth phase and the climatic conditions of the experimental site.

Cultivo de girassol em sistema hidropônico sob diferentes níveis de salinidade

Os sistemas hidropônicos tem se constituído em uma das alternativas para equacionar os fatores naturais adversos à produção agropecuária presentes nas regiões semiáridas do Brasil, como solos rasos, pedregosos e pouco férteis, além da escassez de recursos hídricos em quantidade e qualidade (teores elevados de sais). Este trabalho buscou estudar os componentes de produção do girassol (variedade EMBRAPA 122/V-2000) destinados à obtenção de aquênios e forragem (fitomassa), cultivado em sistema hidropônico, utilizando a fibra de coco como substrato e irrigado com água salobra de diferentes salinidades. O delineamento experimental utilizado foi o inteiramente casualizado, em esquema fatorial 5 x 2 com três repetições, de modo que foram estudados cinco níveis de salinidade e duas densidades de plantio - uma ou duas plantas por vaso. As águas de irrigação foram compostas por 50% da solução nutritiva padrão e 50% de água de abastecimento, adicionada de níveis crescentes de NaCl, resultando em uma condutividade elétrica final da solução (CEs) de 1,7; 4,3; 6,0; 9,0 e 11,5 dS m-1. Verificou-se que a densidade diferenciada das plantas de girassol afetou positivamente os componentes de produção de aquênios e fitomassa da cultura indicando maior viabilidade quando se utiliza duas plantas por vaso.

Modeling of Biological Water and Wastewater Treatment Processes Using Artificial Neural Networks

AbstractA growing world population, unrelenting urbanization, increasing scarcity of good quality water resources, and rising fertilizer applications are the driving forces behind the accelerating upward trend in the use of efficient methods of water and wastewater treatment such as biological processes. Due to the complexity of the reactions in biological processes, a few studies have been performed involving the modeling of biological removal of water pollutants. Thus, the application of the artificial neural networks (ANNs) to predict the performance of the biological systems has been attempted. ANNs are computer‐based systems that are designed to simulate the learning process of neurons in the human brain. One of the characteristics of modeling based on ANNs is that it does not require the mathematical description of the phenomena involved in the process. This review article describes the application of ANNs for modeling of biological water and wastewater treatment processes. Examples of early applications of ANNs in modeling and simulation of biological water and wastewater treatment processes in the presence of various microalgae, macroalgae, bacteria, microbes, yeasts, anaerobic sludge, aerated submerged biofilms, and submerged membrane bioreactors are reviewed.

Estimation of the possible flood discharge and volume of stormwater for designing water storage

The shortage of good-quality water resources is an important issue in arid and semiarid zones. Stormwater-harvesting systems that are capable of delivering good-quality wastewater for non-potable uses while taking into account environmental and health requirements must be developed. For this reason, the availability of water resources of marginal quality, like stormwater, can be a significant contribution to the water supply. Current stormwater management practices in the world require the creation of control systems that monitor quality and quantity of the water and the development of stormwater basins to store increased runoff volumes. Public health and safety considerations should be considered. Urban and suburban development, with the creation of buildings and roads and innumerable related activities, turns rain and snow into unwitting agents of damage to our nation's waterways. This urban and suburban runoff, legally known as stormwater, is one of the most significant sources of water pollution in the world. Based on various factors like water quality, runoff flow rate and speed, and the topography involved, stormwater can be directed into basins, purification plants, or to the sea. Accurate floodplain maps are the key to better floodplain management. The aim of this work is to use geographic information systems (GIS) to monitor and control the effect of stormwater. The graphic and mapping capabilities of GIS provide strong tools for conveying information and forecasts of different storm-water flow and buildup scenarios. Analyses of hydrologic processes, rainfall simulations, and spatial patterns of water resources were performed with GIS, which means, based on integrated data set, the flow of the water was introduced into the GIS. Two cases in Israel were analyzed--the Hula Project (the Jordan River floods over the peat soil area) and the Kishon River floodplains as it existed in the Yizrael Valley.

Strategies for a sustainable management of water resources in horticulture and floriculture

A more efficient use of water resources in agriculture, especially in horticulture and floriculture, is a concerning issue to choose sounder technical and agronomical practices for managing these resources vis-&agrave;-vis: a feasible water economy, the enhancement of natural equilibria and at the same time an increased crop competitiveness. In horticulture, several options are suitable: cultivar choice, timing and type of cropping system, fertilization plan and soil preparation, as well as, weed control and mulching. Micro-irrigation systems play an important role to efficiently reduce water losses and to increase irrigation performance, even if not always are economically feasible in all the cases. The choice of the irrigation management strategy involves a deep understanding of crop water requirements and its responses to water stress, including the identification of critical periods and their economical impact over the crop return. Besides nowadays, there are several new interesting perspectives in the irrigation arena by the employment of moisture sensors (TRD and FDR probes). Considered the scarcity of good quality water resources and its use-competition with other sectors (industrial and civil), for the agriculture will be destinated even all low quality water resources (brackish and wastewater). Within well-delimited standards of quality related to the type of crop and its main use, the use of those kind of water resources would be feasible by adopting and integrating all the possible management strategies, whose choice indeed requires a deep glance on into its cost-benefit.

Hydrodynamic characteristics and sustainable use of a karst aquifer of high environmental value in the Cabrejas range (Soria, Spain)

This paper describes the research carried out in a karst aquifer located in Soria, Spain. The system presents considerable good-quality water resources, yielding a series of springs which constitute a “Natural Monument”. An integral study of the hydrological cycle is presented in order to characterize the hydrodynamic behavior of the aquifer. Research combines conventional geological and hydrogeological approaches with more innovative techniques such as speleo-diving. On the basis of relatively little available data, quantitative results are obtained. These include estimations on porosity, hydraulic conductivity, transmissivity, and groundwater renewal rate and aquifer reserves. A vulnerability assessment is carried out to evaluate the potential effects of overpumping. This is followed by a proposal for sustainable aquifer management. Since aquifers such as the one in this study are frequently found, this methodology could be successfully extrapolated to other cases.

EFFECT OF USING MIXTURE OF DRAINGE AND FRESH WATER ON DRIP IRRIGATION SYSTEMS

The agricultural irrigated area depends on the availability of sufficient quantities of suitable quality of irrigation water, but with the large scale increases in agriculture and the shortage in good quality water resources, lead to the necessity of Using the available water in the most proper way. For that this study was designed to discuss the effect of the type of water on the soil, crops and its effect on the emitters. A field experiment has been applied to study the effect of different irrigation water treatments. Therefore four treatments of irrigation water (100%, 80%, 50% and 0%) irrigation water and the rest is drainage water. Four types of emitters, were chosen to represent the most common types of emitters which exists in the local market, and used in irrigating the vegetable crops, online emitters as HO, inline emitter as GR, pressure compensating emitters as KA and pressure compensating and self flushing as MF. Results showed that the soil was affected by the irrigation water salinity. The water EC increased as well as the pH mainly for the 100% drainage water treatment and this influence decreased for the other three treatments. The MF emitter is the most stable emitter and had a Suitable application efficiency and has not been affected by the irrigation treatment, but its high price eliminate it's use in irrigation vegetable crops, therefore it can be cleared the GR emitter is the most suitable emitter while it came in the second place, but it is not that expensive and available for ordinary farmers. And also the 80% irrigation water & 20% drainage water can be used with little change in the yield than the yield of the irrigation water treatment.

Effect of Evapotranspiration on the Salinity of Wastewater Treated By Aquatic Plants

The shortage of good quality water resources is becoming an important issue in arid and semi-arid zones. Irrigation systems must be developed that are capable of delivering low quality wastewater while taking into account environmental and health requirements. For this reason, the availability of water resources of marginal quality, such as desalinated wastewater, can be a significant contribution to the water supply. We investigated changes in salinity, in conjunction with evaporation kinetics of treated wastewater by aquatic plants. These plants enhance the removal of pollutants by consuming them in the form of plant nutrients and through the microbial activity on their roots. In particular, this treatment applies to urban and agricultural sewage, where treatment units of different sizes can be applied at the pollution source while acting as green environments. In these treatment units, increased salinity due to effect of evapotranspiration (ET) must be managed. The rates of evaporation (E) from the free water surface and transpiration (T) from the plants were determined under field and laboratory conditions. To this end, batch experiments were performed with floating and emergent aquatic plants. After 4 days in the presence of floating plants, the biochemical oxygen demand (BOD) decreased from its 100-110 mg L(-1) initial value down to 30-40 mg L(-1) (65% to 70% removal), concurrent with a 2% to 5% increase in the chlorides level, and 5% to 8% in the electroconductivity. The ET rates were found to be a significant factor in the water balance governing the treatment process. The results of this work provide guidelines for recommended wastewater treatment times that safeguard against undesirable rises in salinity, yet with marginal change in parameters such as BOD. The change of salinity is shown to be relatively minor in the first days of treatment where the change in BOD is faster, whereas in the following days the picture is reversed. This result indicates the advantage of applying shorter treatment periods when the rise in salinity is avoided.

Planning agricultural wastewater reuse in southern Italy: The case of Apulia Region

The future of southern Italian regions lays mainly on conservation and recovery of their peculiar environment (i.e., pleasant climate, beautiful nature and historic heritage). Presently, most of such regions have to face major problems related to water shortage for agriculture and, in some cases, even for drinking purposes. In these regions water shortage is a growing problem and wastewater reclamation and reuse, a key options for their sustainable development, has not yet been implemented at large scale. In these regions, the interest for wastewater reuse is particularly addressed to agricultural and landscape irrigation with the aim of both enhancing the local economy, mostly based on agriculture, and saving good quality water resources for drinking purposes. Referring to the Apulia region, it has many analogies with other areas affected by chronic water scarcity, i.e: the rapid development of local economy, the changes in traditional agriculture practices and land use, the groundwater over-exploitation with consequent sea water intrusion, the climate changes. The mix of all these factors, although with a different weight, has been the main cause of the frequent water shortage problems recorded in the region. Although over the last decades these problems have been partially mitigated by the construction of water transport infrastructures and reservoirs, they are still far to be definitely solved. Because of this, finally, regional authorities have defined a water resources protection and management master plan in which the reuse of treated wastewater, not only in agriculture, plays a relevant role [1]. This paper outlines the local environmental conditions and the rationale supporting such a choice.

Groundwater hydrochemistry at Balkan coastal plains — the case of Marathon of Attica, Greece

The expansion of irrigated agriculture and the overexploitation of groundwater aquifers are leading to seawater intrusion and severe deterioration of groundwater quality at coastal areas. The shortage of good quality water resources constitutes an important threat for the maintenance of productivity of crops and soil protection. In the region of Marathon in Attica, an area with fast urbanization and intense agricultural activity, a network of 56 observation boreholes for monitoring water level and the qualitative characteristics of groundwater was installed. The values of EC, pH, Eh, as well as main anions and cations were determined twice, at the end of rainy and dry periods. Severe deterioration of water quality, due to high salt loads, was recorded, especially in areas very close to the sea. The possible risk for the crops and the soil, deriving from irrigation use of groundwater, was estimated. In certain regions, increased nitrate concentrations were observed due to intense use of fertilizers. The recent prevailing groundwater quality status was compared to that of the previous decade, revealing no significant further degradation of the coastal aquifer, except for some sub-areas.