967 results about "Rainout" patented technology

A system for delivering a humidified gas to a patient is disclosed. The system includes a supply tube having a first supply tube end and a second supply tube end. The supply tube has a first inner diameter. The system also includes an apparatus for delivering heated and humidified gas to the first end of the supply tube and a single lumen having a first lumen end and a second lumen end. The single lumen has a second inner diameter, smaller than the first diameter. The first lumen end is in fluid flow communication with the second supply tube end. The system also includes a nasal cannula in fluid flow communication with the second lumen end. A method of delivering heated and humidified gas to a patient is also disclosed.

The invention discloses a ground daily rainfall predicting method based on satellite remote sensing and regression Kriging. The method comprises the steps that firstly, data are fast obtained through satellite remote sensing, and a regression relation among ground-based observation values, TRMM, DEMs and geographic positions of rainfall capacities of all levels is established according to the classification of the rainfall to obtain regression estimated values and regression residual errors of all levels; secondly, the spatial agglomeration degrees of the regression residual errors of all levels are analyzed, the trend removing is carried out on the regression residual errors, and the Kriging interpolation of the regression residual errors is carried out to obtain the regression residual error spatial distribution characteristics of all levels per 1 km; thirdly, the regression estimated values of all levels and the regression residual errors of all levels are added to obtain the ground-based predicting values of rainfall of all levels per 1 km; lastly, the ground-based predicting values of the rainfall of all levels are merged to obtain a daily rainfall predicting value per 1 km. According to the ground daily rainfall predicting method, the spatial and temporal distribution characteristics of the ground-based rainfall can be accurately predicted, the predicting precision of the ground daily rainfall is improved, the predicted space resolution is improved, and the key problem that the water conservancy department predicts the ground rainfall is solved.

The invention relates to a multifunctional integrated type soil body freezing and thawing test system which comprises five parts including a model bearing system, a temperature controlling system, a water replenishing system, an atmospheric environment simulation system and a data acquisition system. Temperatures of an upper temperature controlling plate and a lower temperature controlling plate in a model box are respectively controlled by a cold bath, a fan and a rotatable sprinkler head are arranged at the top of a box body, and thus simulation of atmosphere rainfall and field wind is realized. the water replenishing system is arranged at the bottom of the box body, a soil sample test section is provided with a temperature sensor, a volume unfrozen-water content sensor, a soil water potential sensor, a heat flux sensor, a deformation sensor and the like, which are used for effectively testing physical mechanical factors such as temperature, volume unfrozen-water content, soil water potential, a heat flux and deformation of a soil sample in a freeze-thawing process, thus measurement precision and range are greatly improved. The defect and the deficiency of size effect caused by small size of an existing freezing-thawing test system are overcome. The multifunctional integrated type soil body freezing and thawing test system is simple in structure, easy to operate, accurate in measurement, low in requirement of a working environment condition, and stable to work.

The invention provides a single frame image rain removing method based on multi-scale feature fusion, Feature extraction of rainless images with different scale receptive fields, then deconvolution operation to get the result of rainless images, using the combination of coarse-scale features and fine-scale features, to promote the rainless images generated by fine-scale to achieve the best effectof rainless. By removing rainlines on multiple scales, the algorithm can be used in a variety of rainwater situations, and the rainout algorithm is more universal. The invention cites the antagonisticerror and the perceptual error to construct a new error function, and trains the rain removing model without any prior knowledge, and does not need to preprocess and post-process the image, thus ensuring the integrity of the whole structure. The results on a plurality of test sets show that the invention can improve the peak signal-to-noise ratio on the luminance signal channel by 2-5dB.

The invention provides a test device and method for simulating the influence of earthquake and rainfall effects on side slope stability. The device comprises an artificial rainfall device, a model box, a vibration table, a test monitoring system and a computer terminal. A flow meter is connected with a water supply main tube; the water supply main tube is connected with a water supply branch tube; the lower part of the water supply branch tube is connected with a rainfall sprayer; a water storage tank is connected with an electronic control valve through a water returning pipe; the model box is located below the rainfall sprayer; the model box is fixedly connected with the vibration table. The method comprises the steps that in the test, a high-definition digital image processing technique is used to track and observe the displacement change of side slope soil body; at the same time of camera shooting in the whole process, after the earthquake and rainfall effects, positions having abnormal situations of the side slope side and the side slope surface are observed and recorded; classification and integration and analysis are conducted on the collected data to obtain a side instability mechanism under the coupling effects of earthquake and rainfall. The test device and method have the advantages of carrying out related experiments of single earthquake, single rainfall, and the coupling effects of earthquake and rainfall; being simple in structure and low in test cost.

The invention discloses a method of implementing an automatic control and storage device used for collection of natural rainwater or rainfall runoff, relating to the fields of environmental protection and water supply and drainage work. According to the invention, by a single-chip microcomputer control device, parameters such as rainfall, rainfall time or flow are taken as trigger conditions, rainwater of different characteristic stages in a rainwater collector can be stored into different independent sampling bottles by automatic control. The rainwater collector is connected with a submersible pump to collect the rainfall runoff, and also connected with a rainwater receiving funnel to collect the natural rainwater. A distributor on the rainwater collector can automatically fill the rainwater in the rainwater collector. The device has the characteristics that firstly, the device is suitable for the fields and occasions without an alternating current power source, remote transmission of data can be automatically controlled, and a possibility of unattended automatic collection of rainwater sample in the fields at night can be achieved; secondly, the rainwater of different stages can be automatically collected according to the given rainfall or time, and the device is suitable for monitoring the change of water quality of the rainwater along with factors such as rainfall and time; thirdly, rainwater under various conditions such as natural rainwater and rainfall runoff at different catchment areas can be collected.

The invention relates to a tide predicting method for the tide is influenced by various factors, including cyclical factors, such as tidal generation force, and non-cyclical factors, such as wind power, atmospheric pressure, coast characteristics, rainfall, dip angles of the lunar orbit and the like. The predicting accuracy of the traditional harmonic analysis method is influenced by partial tide number, and the traditional harmonic analysis method cannot analyze the influence of non-cyclical factors; the artificial neural network method developed recent years overcomes the defect that the non-cyclical factors cannot be predicted by the harmonic analysis method to a certain extent, but has great data volume required by study training samples and wide involve range, can cover various possible conditions, but has less station historical data of non-cyclical factors. The invention provides a predict model, wherein factors which influence tide non-cyclically, such as wind directions, rainfall, storm surge, coast characteristics and the like, can be fused into the model, and small sample data can receive more accurate results. In the method, a support vector machine (SVM)-based predict model is established, wherein, an SVM toolbox is imported into MATLAB 7.8; training sample data is trained by utilizing svmtrain function; the formed model is tested by using a test sample svmpredict function; and the trained and tested data can predict the tide in the same tide test station.

The invention discloses a dry-wet circulation climate hypergravity simulation system. According to the present invention, an air heating dehumidifier, an air blower and a water tank are arranged in the external of a hypergravity centrifuge-carried model box; a gas outlet of the air heating dehumidifier is connected with a gas inlet of the air blower through gas guiding pipes; a gas outlet of the air blower is connected with a gas inlet pipe; a gas inlet of the air heating dehumidifier is connected with a gas outlet pipe; the water tank is fixed on the top of the model box; the gas inlet pipe and the gas outlet pipe both extend to the internal of the model box; a rock-soil mass model is arranged on the bottom of the internal of the model box; an earthwork separator is arranged between the rock-soil mass model and a side wall of the model box, and the left space between the earthwork separator and the side wall of the model box is provided for a water collecting area; a water outlet is arranged on the bottom of the water collecting area; quadrate rain-fog nozzles are arranged above the rock-soil mass model, wherein the quadrate rain-fog nozzles are distributed in matrix; each quadrate rain-fog nozzle is communicated with the water tank through water transporting pipes; pressure sensors, pressure reducing valves and rain controlling switches are arranged on the water transportingpipes; the pressure sensors and the pressure reducing valves are arranged outside the model box.

The invention discloses a rainfall field reconstruction method by integrating microwave link, disdrometer, rain gauge and weather radar: selecting microwave link, disdrometer, rain gauge and weather radar to synchronously observe areas covered and make disperse lattices; making space matching and time matching over data of rainfall intensity synchronously observed by disdrometer, rain gauge and weather radar and making interpolation by inverse distance interpolation to draw lattice data; reconstructing rainfall field by lattice data of rainfall intensity synchronously observed by microwave link, disdrometer, rain gauge and weather radar: evaluating autocorrelation coefficient and cross-correlation coeffi-cient of data of rainfall intensity synchronously observed by microwave link, disdrometer, rain gauge and weather radar by recursion of estimated value in time domain to further determine variance of microwave link, disdrometer, rain gauge and weather radar; estimating and determining best weight of four kinds of data of rainfall intensity by minimum variance to realize rainfall field reconstruction.

Systems and methods for reducing the visibility of rain in acquired images are provided. One or more inputs relating the scene desired to be acquired by the user are used to retrieve camera settings that will reduce the visibility of rain in acquired images. Additionally, features relating to the scene may be automatically determined and used alone, or in combination with user inputs, to retrieve camera settings. The acquired images may be part of a video. Another feature of the invention is its use as a rain gauge. The camera settings are adjusted to enhance the visibility of rain, then one ore more images are acquired and analyzed for the amount and size of raindrops. From this analysis the rain rate can be determined.

The invention provides an earthquake early warning method based on Internet of Things multi-sensor information fusion and a neutral network technology, which comprises the concrete steps of firstly performing networking fusion on the multi-sensor information of multiple earthquake parameter monitoring points by the Internet of Things technology, wherein the information comprises soil radon alpha energy spectrum, well radon alpha energy spectrum, temperature in soil, humidity in the soil, air pressure in the soil, surface temperature, surface humidity, surface air pressure, surface wind speed, surface rain fall, well water level, well water temperature, well water turbidity, well water mercury, well water carbon dioxide, earthquake sound, earthquake tilting and the like; then obtaining abnormal information feature vectors by wavelet analysis, a correlational analysis method, a feature tree search method, a non-linear quantifying and processing method and a main component analysis method; and finally obtaining the relation between the multi-sensor information abnormality and an earthquake by the neutral network technology, thus achieving the aim of predicting the earthquake. The technical scheme of earthquake early warning method based on the Internet of Things multi-sensor information fusion and the neutral network technology is feasible and convenient to implement and can achieve the aim of more accurately predicting the earthquake.

The invention discloses a glacial lake burst early-warning method. Aiming at the defects that the adopted index is not reasonable, modification on observation data is over-simple in the existing glacial lake burst early-warning method, the invention provides the glacial lake burst early-warning method comprehensively considering the affects from an atmospheric temperature and the rainfall condition. According to the method, long-term observation data of temperature and rainfall in an observatory station is obtained and analyzed by a control center, a cumulative positive temperature daily increasing speed value TV in early days of a forecast date and a rainfall daily increasing speed value RV in early 30 days of the forecast date are calculated, and the TV value and the RV value are simultaneously subjected to double-index comparison with a burst warning curve RV=2.7214TV<-0.956> to judge the burst risks of the glacial lake, and an alarming system is started by the control center if necessary. According to the method, the corresponding relationship between two specific indexes of the cumulated temperature daily increasing speed value and the rainfall daily increasing speed value in early 30 days which are selected from numerous temperature and rainfall indexes and the glacial lake burst danger is determined, and the burst early-warning curve is determined. The forecast is carried out according to a more comprehensive and reasonable climate index, so the early-warning effectiveness is increased.

The invention provides an interpretable short critical extreme rainfall prediction method based on an attention mechanism. The interpretable short critical extreme rainfall prediction method includesthe steps: firstly, screening use parameters through a random forest; calculating a standard precipitation index (SPI) of the to-be-measured station; forming a new matrix by the standard precipitationindexes and the selected parameters and inputting the new matrix into a long-term and short-term memory network for training; adding an attention mechanism into the neural network; visualizing weightcalculation of the attention mechanism in the training process; and finally, predicting the rainfall of the target area in the future 3, 6, 9 and 12 hours by taking 3 hours as a unit, wherein an attention mechanism is used in the prediction process to optimize the situation of short-term heavy rainfall, so that the prediction capability of the model for extreme weather is improved, and meanwhile,the interpretability of the model is also enhanced.

The invention discloses an urban drainage basin flood prediction method and system. The method comprises the following steps: determining rain pattern space-time distribution of an urban area according to historical data; establishing a flood simulation scene library by simulating parameters of the region under different scenes by using a refined flood model according to the rain pattern spatial and temporal distribution and the river flood boundary conditions; establishing a rainstorm flood relational expression and a waterlogging simulation relational expression based on the simulation data; correcting the obtained forecast rainfall data according to the rainfall pattern spatial and temporal distribution, and dividing different scenes; and performing data matching on the rainstorm flood relational expression, the waterlogging simulation relational expression and different scenes, and when the matching degree is greater than a preset value, taking simulation data in the flood simulation scene library as urban drainage basin flood forecasting information. According to the method, the flood peak flow and the total flood amount of each node in the prediction period, and information such as the ponding point position, the ponding depth and the ponding duration can be rapidly calculated, rapid prediction, research and judgment of urban flood disasters are achieved, and precious time is gained for flood control and drainage emergency management.

The invention provides a rainfall estimation method based on microwave rainfall attenuation, which comprises the following steps: acquiring microwave rainfall attenuation data of an estimation area and corresponding rainfall data, and obtaining a rainfall estimation result to be corrected through a microwave rainfall inversion model; acquiring multi-source non-rainfall data corresponding to the rainfall data, training a deep belief network by using the multi-source non-rainfall data and the microwave rainfall data set, constructing a correction and optimization model, and performing correctionand optimization on estimated data output by the microwave rainfall inversion model; obtaining a preliminary rainfall estimation result of the estimation area through the microwave rainfall inversionmodel according to estimation request parameters proposed by a user, and carrying out the correction and optimization of the preliminary rainfall estimation result according to the correction and optimization model, so as to obtain a final rainfall estimation result of the estimation area. The invention also provides a rainfall monitoring system based on microwave rain attenuation and a data processing device for rainfall estimation by using the rainfall estimation method.

The invention discloses a measuring method and an implementation device for a slope surface runoff and comprises a terminal processing unit connected to each unit and used for collecting data information of each unit; a slope surface water collecting unit arranged on the earth' surface of the slope surface and used for collecting rainfall on a slope surface; a flow detection unit connected to a slope surface detection unit and used for measuring the water quantity of the collected rainwater at real time; a water storage measurement unit connected to the flow detection unit and used for measuring the water quantity of the collected rainwater at real time. The invention has the advantages of simple structure, convenience in use and strong stability of the device. Due to the adoption of a double measurement structure, so that measurement accuracy is greatly improved, a wireless transmission module is provided in the device, and a measurement result can be transmitted remotely, and a real-time performance is greatly improved. Two electromagnetic valves are provided for the invention, so that safe and stable operations of a system can be guaranteed.

The invention belongs to the field of hydraulic and hydro-power engineering, and relates to a method for measuring the intensity of atomization rainfall formed by flood discharge in hydropower engineering. The method comprises the following steps of: collecting atomization rain by using two or three rain collecting tanks, wherein the shapes of the inlets of the rain collecting tanks is completely same, and each inlet plane is vertical to each other on space; respectively gathering the collected rainfall in corresponding water measuring tank by independent guide pipes to measure the intensity of the rainfall, and finally, calculating by subjecting the measured intensity of rainfall to a vectorial resultant to obtain the corresponding total atomization rainfall intensity and the rainfall direction. The method disclosed by the invention can be used for the observation of a model and a proto-model of the atomization rainfall in hydropower engineering, and the measured rainfall intensity data is excellent in regularity and high in precision, so that the research on the mechanism of atomization of flood discharge is prompted greatly, the atomization forecast accuracy of hydropower station engineering is enhanced, and the reliable guarantee is provided to the prevention of the disaster of atomization of flood discharge.

The invention relates to an adjustable and controllable simulated rainfall device, and belongs to the technical field of artificial rainfall. The adjustable simulated rainfall device comprises lifting systems, a rainfall system, a control system and a water supply system, wherein four sets of lifting systems are provided, and construct four support legs of the device; the rainfall system consists of rainfall rods; the control system comprises two stepping motor chain wheels, two stepping motors, a rainfall angle adjusting chain, a solar panel, a rainfall angle adjusting chain wheel, a rainfall angle tail end controller, a rainfall density tail end controller, a rainfall density adjusting chain, a pressure roller base, a pressure roller and a rainfall density adjusting chain wheel; and the water supply system comprises a telescopic hose, an adjustable one-way valve, a speed regulating motor, a hydraulic motor, a water pipe and a water tank. The adjustable and controllable simulated rainfall device is convenient to install, the rainfall density and the raindrop falling angle can be changed at any time, the rainfall uniformity is high, natural rainfall in different areas under different climate conditions can be well simulated, and the research of water and soil loss under variable rainfall conditions is well facilitated.

The invention discloses a probability distribution based short-time rainfall forecast method and system, and belongs to the technical field of rainfall forecast. The system comprises a cloud atlas collection module, a meteorology data acquisition module, a data transmission module, a master control module, a rainfall probability generation module, a precipitation estimation module, a rainfall characteristic determination module and a data display module. The precipitation estimation module can obtain rainfall data of higher precision and confidence by using advantages of multi-source data; therainfall characteristic determination module uses a rainfall rain type characteristic matrix and time characteristic matrix of a rainfall station to describe the rainfall and movement condition of the rainstorm center in the aspects of time and space; and a mathematic matrix is used to describe the time-space distribution characteristic of rainfall, the rainfall characteristic is researched lateron the basis of the mathematic matrix, and the accuracy and comprehensiveness of rainfall characteristic research are improved.

Systems and methods for reducing the visibility of rain in acquired images are provided. One or more inputs relating the scene desired to be acquired by the user are used to retrieve camera settings that will reduce the visibility of rain in acquired images. Additionally, features relating to the scene may be automatically determined and used alone, or in combination with user inputs, to retrieve camera settings. The acquired images may be part of a video. Another feature of the invention is its use as a rain gauge. The camera settings are adjusted to enhance the visibility of rain, then one ore more images are acquired and analyzed for the amount and size of raindrops. From this analysis the rain rate can be determined.

The invention discloses a landslide short-term and temporary intelligent early warning method based on an XGBoost algorithm, and relates to the field of landslide monitoring and early warning and machine learning. The XGBoost algorithm is applied to the field of landslide short-term and temporary intelligent early warning for the first time. The method specifically comprises the following steps: acquiring landslide body feature data in real time to construct landslide body feature vectors, wherein the landslide body feature vectors comprise rainfall, soil moisture content and landslide body surface deformation features; allowing the XGBoost model to predict the landslide body surface deformation characteristics of the prediction day according to the landslide body characteristic vectors constructed by the historical time sequence before the prediction day and the rainfall predicted by the weather forecast of the prediction day; and if the prediction value is greater than the safety threshold, sending out intelligent early warning. According to the method, the calculation speed and the prediction precision are obviously improved, and intelligent short-term and temporary prediction can be carried out on landslide deformation based on future rainfall prediction data.

The invention relates to a triggering ultrasonic tipping bucket rain gauge which comprises a rain collector, a funnel, a tipping bucket, magnetic steel, a reed switch, a ship bucket, a water inlet pipe, a metering cylinder, an ultrasonic water level measuring controller, an electric valve, a water outlet pipe, a base support and an outer barrel. The rain collector collects natural rain, the rain is gathered and flows into the tipping bucket through the funnel, the tipping bucket turns over and pours rainwater in the water inlet pipe and the electric valve through the ship bucket, the rainwater flows into the metering cylinder, the ultrasonic water level measuring controller measures the water level in the metering cylinder, and the water level is converted into rainfall and output. When the water level in the metering cylinder reaches a certain height, namely 10-mm rainfall, the ultrasonic water level measuring controller closes a water inlet valve to prevent the rainwater from entering the metering cylinder, a drainage valve is opened at the same time to drain the rainwater in the metering cylinder through the water outlet pipe, the drainage valve is closed after the rainwater is drained, the water inlet valve is opened, the rain flows into the metering cylinder to be measured, the steps are repeated for measuring, and the rainfall is accurately measured.

The invention discloses a satellite retrieval method for night rainfall probability, which comprises two steps of rain area division and rainfall estimation. A rain area division method comprises the steps of establishing an RPIM (rainfall possibility identification matrix) and then obtaining rainfall probability of all kinds of combination of brightness temperature Tb1 and brightness temperature Tb4-1 in the RPIM, wherein the RPIM is established based on an IR1-BTD41 two-dimensional spectral space. Therefore, an estimated rainfall value obtained through the rain area division method and a rainfall estimation method provided by the invention can be better related to and be more slightly deviated from an actual rainfall value, i.e. the estimated rainfall value is better consistent with the actually measured value, so the satellite retrieval method for night rainfall probability has the advantage of better application to multi-spectral satellite image night rainfall retrieval and nowcasting.

The invention relates to a new method and system for detection and removal of rain from video using temporal / spatiotemporal properties. Advantageously, the temporal / spatiotemporal properties are involved to separate the rain pixels from the non-rain pixels. It is thus possible by way of the present invention to involve less number of consecutive frames, reducing the buffer size and delay. It works only on the intensity plane which reduces the complexity and execution time significantly along with accurate rain detection. This new technique does not assume the shape, size and velocity of the raindrops which makes it robust to different rain conditions. This method reduces the buffer size which reduces the system cost, delay and power consumption while maintaining sufficient quality of rain detection.

The invention discloses a debris flow rainfall I-D curve threshold construction method and a debris flow early warning method. The I-D curve threshold construction method comprises the following stepsof firstly, acquiring basin underlying surface data required for a Richard model and Van Genuchten equation numerical simulation; starting a hydrologic simulation process under a given rainfall intensity condition; determining the stability and the runoff generation state of each grid in a drainage basin along a time sequence, and calculating the bulk density of a water and soil mixture; and recording data according with a control point to fit an I-D curve, and finally acquiring a set of I-D thresholds under a previous rainfall amount condition. The invention simultaneously provides a corresponding drainage basin debris flow early warning method. By using the method of the invention, the idea of fitting the curve through historical data statistical analysis is abandoned, and the breakthrough of constructing a debris flow generation condition threshold from the aspect of the measurement of the dynamic index of a debris flow characteristic is realized. The method can effectively solve the problem of using the I-D curve threshold to implement debris flow early warning in the drainage basin without data.

The invention relates to a geological disaster prediction and forecast technology, and aims to provide a rainfall threshold analysis method causing basin landslide risks. The method comprises the following steps: establishing a three-dimensional grid according to DEM topographic data and soil layer thickness data of a target watershed, and generating boundary conditions and initial conditions required by an RIRM hydrological model; calculating space-time changes of hydrological elements in the drainage basin and drainage basin slope stability reference indexes of any three-dimensional positionin the drainage basin; drawing a relation curve that the safety factor SF, the landslide volume and the landslide area respectively change along with time under the conditions of different rainfall durations and different rainfall intensities; analyzing the relationship between landslide deformation damage and rainfall to obtain rainfall thresholds causing basin landslide risks under different conditions. According to the method, natural basin geomorphic hydrological response characteristics are reserved, and prediction errors can be effectively reduced; drainage basin hydrology and slope stability analysis can be carried out simultaneously, the actual occurrence process of drainage basin landslide disasters is met, and the prediction result is more real and reliable.

The invention provides a method for reconstructing a vertical rainfall field based on satellite-ground link scanning, and the method comprises the steps: building a plurality of satellite signal receiving ends to receive polar orbit satellite signals, and forming a plurality of satellite-ground links; meshing a vertical region to be reconstructed; obtaining the spatial distribution of attenuationcoefficients by analyzing the relation among satellite-ground link signal strength information, rainfall attenuation coefficients and satellite-ground link lengths, performing the inversion of the spatial distribution of rainfall according to a relation model of the attenuation coefficients and the rainfall strength, and generating rainfall information in a vertical space; and finally, reconstructing the vertical rainfall field by combining with a detection area. The method not only makes up the defects of the traditional means for detecting the vertical rainfall field, but also has the advantages of high temporal-spatial resolution, low cost and the like, and provides important data support and guarantee for water resource management, agricultural development, natural disaster early warning and the like.

The present invention relates to a water collection system, which blocks down-pipes to collect water from a roof. A down-pipe (27) is located adjacent a rain water diversion unit (31). The unit comprises a box (36) with the down-pipe (27) fitted to an opening (37) in bottom (38) of the box (36). The gutter (14) has two side-by-side openings (39 and 40), the opening (40) has an overflow in the form of upstanding wall (41) while the opening (39) has a valve plate (42) hinged to the front edge at (43). A pneumatic actuator (44) is used to move the valve plate (42) to the closed position. When the valve is closed, the opening (40) and the upstanding wall (41) serve as an overflow back to the stormwater via the box (36). The tank pipe (17) also has an opening (45) with an upstanding wall (46) which has its upper edge (47) set lower than the upper edge (48) of the wall (41) of the overflow. All down-pipes are fitted with diversion units. A controller includes a rain sensor to detect a rain event whereupon a time delay is imposed for first flush to flush the roof before the valves close the down-pipes. When the tank is full a float is used to operate the controller to open the valves if they are closed or prevent them closing in the case of a new rain event and the tank being already full.