Constructing Water Balance

Introduction
To understand the water regime of a specific area for water resource planning one of the first tasks is to understand the water balance of that area. Water balance is a budgeting exercise that assesses the proportion of the rainfall that becomes stream flow (or runoff), evapotranspiration, and drainage (or groundwater recharge).


Objectives of Water Balance Demonstration
1. To introduce the reader to a simple water balance model, namely, the Thorntwaite-Mather model, henceforth referred to as the T-M model (Thorntwaite et al, 1955;1957; Steenhuis et al, 1986);
2. To provide the reader with the tools to construct a water balance for her/his own region of interest, with the help of video tutorials and a sample Excel spreadsheet that can be downloaded and modified.

This document is intended for general instructive purposes for an audience that has some basic knowledge of water resources and associated terminology. No advanced expertise should be needed to understand and use this tutorial.

There can be various models to construct water balance of an area; the model that is used here for demonstration is T-M Model which has an advantage of being one of the most simple models. It can be used to determine a general estimate of the water balance regime, for individual fields to small watersheds.

Applications and Limitations : However, as in all scientific investigation, this tutorial should be used responsibly and with a full knowledge of the user's specific study area. This model and its variants have been used, for example, for irrigation scheduling of individual fields, water budgeting of small watersheds, generating actual evapotranspiration estimates for comparison with other methods - to name a few applications.

Being a lumped model, in the form described, the T-M model does not provide spatially distributed predictions, nor does it perform flow routing routines.

Composting toilets – the future of sanitation?

Ask any water supply board engineer and he will tell you that the bigger headache is sewage management and not water supply. Statistics will also show that almost all of India has access to water supply –of varying quantity and quality no doubt- but far too few have access to good sanitation.
The Millennium Development Goal adopted by the UN in September 2000 and of which India is a signatory seeks to halve the number of people without access to sanitation by 2015. That means India will have to build at least half of 115 million toilets to cover half of 78% of our rural population and 24% of its urban population un-served sanitation units by the year. A huge task indeed.
Typical sanitation solutions have included the septic tank or simply a pit latrine. Both tend to pollute ground water and are environmentally unsatisfactory. Even in water resource rich area like Goa or Kerala inadequate sanitation has ended up contaminating ground water to such an extent that many wells are unusable. Sanitation and water supply are inextricably linked. If it is not ‘fouling the nest’ it is the unavailability of water which has made many toilets unusable in rural area. If you do not have water to drink will you use it for a toilet?

On the other hand area wide underground sewerage systems with treatment facilities are difficult to provide and are costly ventures. They tend to be energy consuming and generally do not work satisfactorily. For scattered houses in outlying areas of cities, in villages, in places with a high water table and in hard rock area technically appropriate solutions are either not available or are costly to implement.
In such a scenario one emerging solution is a dry composting toilet. A composting toilet collects human waste and converts it to a fertilizer resource for plant growth without polluting water bodies or groundwater.

One such urine separating composting toilet system looks like this

An Eco-san separating pan



Tin drum for faeces and barrel for urine collection


The front portion of the pan is for the urine and the rear part with a cover is for the faeces, much like the plumbing system in human beings. After using the toilet the faeces is covered with sawdust. If toilet papers are used they are also put in the portion where the faeces go, alternately wash water can also go there. The important point is to cover the used portion completely with sawdust. The toilet is surprisingly a no smell toilet and there are no other problems of flies, gnats or insects. The urine is collected in a plastic barrel and after dilution with water in proportions of 1 to 3 or 1 to 8 can be used for plants, especially trees, where it makes a good fertilizer with its high nitrogen content.

The faeces is collected in a tin box and once the tin box is full it is replaced
with another. The full box is allowed to compost for 3 weeks and then transferred for further composting to either a large composting drum or to to an earthen pit. When covered with leaves the material composts very well in about 3 to 6 months and can be used as a soil nutrient.
Waste composting in two tin drums
below the rain water collection drum

Tippy tap’ for washing with minimum water

For washing purpose a ‘tippy tap’ – a product developed by the Centre for Applied Rural Technology, Mysore- can be used with which the wash job can be done along with hand cleaning with as less as 80 ml of water. The ‘tippy tap’ can be placed in the toilet for washing along with a saw dust container for covering the faeces.

This ecological method of sanitation consumes less than a litre of water per day for a family, converts human waste to a fertilizer resource, is clean, hygienic and functional and can be constructed almost anywhere irrespective of high water tables, hard rock below the ground or any other conditions which prevent the construction of regular toilets. By harvesting water from the rooftop of the toilet into a simple 200 litre drum all the water requirement of washing in the toilet can be met by the toilet roof itself.
Rooftop rain collected in a 200 litre drum for use in Eco-san

The urine separating WC’s are available not only in the Indian type but also in the European type. These toilets are being used in individual houses as well as flats.Eco-san alternatives are coming up in many places in the world including Sweden, Germany, Denmark, the USA, China and Sri Lanka to name a few. India too has its Eco-san heroes in Dr Bindeshwar Pathak of the Sulabh movement and Paul Calvert in Trivandrum, Kerala.

S.Vishwanath and Chitra Vishwanath
www.inika.com/chitra
www.rainwaterclub.org
For more information log on to www.rainwaterclub.org or call 080-23641690.

Water Trading in China: A Step Toward Sustainability

In recent years, scarcity and pollution of water have become the paramount environmental woe in China. Numerous reports and books have exposed China's water crisis, depicting a nation suffering in the face of black-running rivers and dried-up waterways. Nationwide, the per capita availability of fresh water is only one-quarter of the world average.
But a new regulation from the nation's water authority may hold the key to achieving water sustainability in this thirsty country. The Interim Measure for Water Quantity Allocation, which came into effect on February 1, provides a framework for allocating water rights across provinces, autonomous regions, and municipalities that are under the direct jurisdiction of the central government. The ruling's 17 stipulations lay out the principles, mechanisms, and practices for water allocation, potentially opening Chinese markets for water trading and enabling the use of market tools to promote conservation.

The need for better delineation of water rights in China has become increasingly urgent. Water demands within shared river basins are frequently at conflict due to industrial expansion and urbanization. During a drought in 2006, Chongqing municipality in western China saw a dramatic decline in flows from the Jialing River, the city's main water source, despite the fact that the river's upper reaches had received plenty of rain. The shortage was triggered by the more than 50 dams upstream from the city, which had retained the water for power generation. Such competing claims are prevalent in nearly all of China's major river basins.

As water demands keep rising, water waste remains pervasive due to the current "open-access" nature of China's water resources. According to statistics, in 2003 China's utilization coefficient for agricultural irrigation water was only 0.4-0.5, compared to 0.7-0.8 in industrial countries. Water use per unit of gross domestic product was as high as 413 cubic meters, four times the world average, while water use per value added of industry was 218 cubic meters, 5 to 10 times the level in industrial countries. China's industrial water-recycling rate was only 50 percent，compared to 85 percent in industrial countries.

The traditional practices of promoting conservation through education, moral suasion, and technological innovation are no longer able to keep up with China's rising water demand. By allocating water rights and introducing market-based tools, the new regulation may accelerate progress toward water saving, protection, and pollution control.
The regulation is a response to several successful trial efforts over the past eight years. In 2000, China saw its first case of water trading between Dongyang City and Yiwu City in Zhejiang province, with the latter buying some 50 million cubic meters of water annually from the former at a price of 4 RMB (US$0.57) per cubic meter. The pact resulted in a win-win situation in early 2005, following a serious drought in Yiwu City. Yiwu avoided the significant cost of having to build its own reservoirs, while Dongyang received funds for maintaining its existing reservoirs and water infrastructure.

Since then, China has launched trial projects in several regions, including Ningxia, Inner Mongolia, and Ganxu in the northwest; Jiangxi and Chongqing in the west; Shanxi in the middle region; and watersheds covering Beijing and Hebei. The projects are either local initiatives spurred by acute water crises, or efforts by the central government to promote water savings.

The success of these projects has given policymakers confidence to explore bolder national schemes, resulting in the recent water-rights regulation. If effectively enforced, the ruling could be as significant as China's widespread land reforms in the 1950s, which freed up rural labor and made it possible to feed the nation's 1.3 billion people. Although much implementation work remains to be done, the regulation is a bold first step toward sound water management in China.

by Yingling Liu

Yingling Liu is manager of the China Program at the Worldwatch Institute, a Washington-D.C. based environmental research organization.