Weather modification, solution and innovation to reservoirs water sustainable management (case study: ZayandeRoud reservoir)

Climate change has had devastating effects on water resources in many countries. Many volumes of Iran's water resources have declined due to climate change. Meanwhile, the use of weather modification methods, especially cloud seeding, is a practical solution to adapt to the climate change impact. In Iran, consecutive droughts and climate change have reduced water resources of dams behind and in some cases, they have completely dried up. Nowadays, cloud seeding is used as the most costeffective method for water harvesting in the world... The results of the evaluation of cloud seeding projects in most parts of the country indicate an average runoff increase of between 10% and 15% during the seeding periods. Zayanderud Dam is one of the big dams in Iran in the Zagros Mountain range its water resources have been significantly reduced by overdraft and climate change. Cloud seeding operations have been performing for many years in the Charmahal and Bakhtiari catchment, which are located upstream of the ZayandeRoud reservoirs as new method to sustainable water resources management of dams. In this article, the results of runoff production by cloud seeding operation will be noted in the ZayandeRoud Dam for 10 years Non-consecutive (2006 – 2016). * Corresponding author: s.poormohammadi@gmail.com © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/). E3S Web of Conferences 346, 03023 (2022) https://doi.org/10.1051/e3sconf/202234603023 Sharing Water: Multi-Purpose of Reservoirs and Innovations


Introduction
Iran has a hot, dry climate characterized by long, hot, dry summers and short, cool winters. The climate is influenced by Iran's location between the subtropical aridity of the Arabian Desert areas and the subtropical humidity of the eastern Mediterranean area. January is the coldest month, with temperatures from 5°C to 10°C, and August is the hottest month at 20°C to 30°C or more.
In most of the areas, summers are warm to hot with virtually continuous sunshine, but high humidity on the southern coastal areas of the Persian Gulf. Daily Temperatures can be very hot; on some days temperatures can reach easily 40°C or more, especially along the Persian Gulf and Oman Sea which causes a danger of heat exhaustion.
About 70 percent of the average rainfall in the country falls between November and March; June through August are often rainless. Rainfall varies from season to season and from year to year. Precipitation is sometimes concentrated in local, but violent storms, causing erosion and local flooding, especially in the winter months. A small area along the Caspian coast has a very different climate; here rainfall is heaviest from late summer to midwinter but falls in general throughout the year. Therefore, Iran Can be divided into 3 major climate areas ( Fig. 1): -Mediterranean climate, which covers the narrow strip alongside Caspian Sea in the north -Cold dry climate in the mountain areas of the west and Northwest, -Arid (or desert) and semi-arid climate, which covers most of the country, especially the central plateau of Iran. -Also, the average long-term precipitation of the country is 220 mm, with a nonuniform spatial and temporal distribution across the country. Weather modification-A weather modification (also known as weather control) is the act of intentionally manipulating or altering the weather. The most common form of weather modification is cloud seeding, which increases rain or snow, usually for the purpose of increasing the local water supply. [1][2][3] Weather modification can also have the goal of preventing damaging weather, such as hail or hurricanes, from occurring; or of provoking damaging weather against the enemy, as a tactic of military or economic warfare like Operation Popeye, where clouds were seeded to prolong the monsoon in Vietnam . 2 Also, existing literatures shows that cloud seeding technology is an economic option for water harvesting, compared with other possible solutions like desalination technology, wastewater treatment, artificial recharge and etcetera. For instance, Shivaji (in two thousand five) stated that costs of cloud seeding operations are about fifteen US dollars per one thousand cubic meters of enhanced water. Table 1 shows these cases.

Table1. Costs of different methods for water harvesting (Source: Shiva, 2005)
The goal of this research is introduction of cloud seeding project in Iran and assessment of rainfall increasing to Zayanderoud basin.

Weather modification operations in Iran
The process of performing the cloud seeding operations is as follows (Fig. 2): at the first, based on output of weather forecast models, current weather data and weather radar & satellite images are decided to perform operations and the right time and place for seeding is determined. During the flight, the operational team will closely monitor the cloud system with the help of airborne sensors and real-time information sent from the Air Operations Control Center and begins to seeding. Immediately after the operational season all seeding flights are evaluated. Inter-basin transfer 400 Artificial Recharge 230 Wastewater Treatment 220 Cloud seeding 15

Row
Operation

Equipment and services
The cloud seeding programs in Iran include the airborne method for the cold clouds, and the airplanes are equipped in order to be able to seed above and inside the clouds. The material used in Iran cloud seeding programs, is silver iodide for seeding the convective clouds and liquid nitrogen for seeding the stratiform clouds. Silver iodide acts as ice nuclei and with the initiation of the Bergeron's process, leads to the production and enhancement of the ice crystals and the subsequent speed up of the precipitation process. Liquid nitrogen also acts as a coolant and with decreasing the environment's temperature, leads to the freezing of the liquid droplets inside the cloud and forming the ice crystals (see the first chapter). Figure 3 shows two aircrafts dedicated to the cloud seeding in the Yazd International airport and in part B, Liquid propane tank (cloud seeding agent). There are two Antonov-26 aircrafts which are used for the cloud seeding in Iran. The equipment mounted on these two aircrafts includes two sets, one for sensing the meteorological quantities, and another for injecting cloud seeding material inside the clouds. Fig. 3. A) Two aircrafts dedicated to the cloud seeding in the Yazd International airport. B) Liquid propane tank (cloud seeding agent).

Evaluation
Determination of control stations: Maximum destination between stations of control region and target region's border should be 50 km to 100 km and should be located in areas which continentally are similar to the target region. Precipitation volume of January, February, April and December of 2009-2010 was measured through kriging method and related raster maps were made through normal kriging method and total volume of precipitation for target region was specified. Time series of monthly precipitation for each station for exact time periods was provided and was take in to regression model, as independent transitive.

Historical regression approach
According to national and international evaluations, historical regression is one of the most reliable approaches in cloud seeding project's evaluation. In this approach, best regression proportion between control and target region during years which no cloud seeding has been done, is determined so that having precipitation volume of control region, the precipitation of target region can be prospected. In this approach, proportion data between control and target region can be very variable and possibility of estimating the changes to be accidental is probable. One of preparations which should be done before evaluation is to normalize monthly precipitation data. If the actual data is not normalized, the presumption of mistakes in adherence of changes in regression line from normal line will be common. The other point which should be considered precisely is equality of time scale between control and target region. If the time scale in both regions is not equal, correlation and reliable estimations are doubted.

Determination of precipitation in target area
First, raster maps for each month of the year  were generated using interpolation kriging method and then precipitation values for each year were extracted from these maps. In the next step, the precipitation volume of December, January, February and April for target stations were calculated and (using interpolation method) used as dependent variables for estimation of precipitation volume of target regions.

Determination of confidence levels:
In creditable sources, the confidence level of results of cloud seeding projects is determined to be 95%. So, to determine that in confidence level of 95%, the increase of precipitation is caused by cloud seeding or any other factor has effect on this increase, some other confidence tests will be done on results.

Determination of confidence intervals:
The determination of confidence intervals of natural changes in precipitation of region is achieved through statistic methods. For better understanding of effect of confidence intervals on confidence of results, it can be said that if precipitation volume in target region (seeding materials affected area) is higher than prospected volume, it means that this increase (with confidence of 95%) is caused by cloud seeding project and if precipitation volume is lower than minimum prospected volume, it means that (with confidence of 95%) the cloud seeding project has caused reduction of precipitation, also if the precipitation is within prospected volume, it means that the effect of cloud seeding project can't be judged. Table 2 shows Information on evaluation of projects in Zayandehrud catchment area from 2006 to 2017. As  table 3 Table 4 shows the results of our analysis on enhanced volumes of water and costs of cloud seeding activities for the Central Iran Cloud Seeding Projects during two thousand fifteen (2015). This project covered five provinces of Yazd, Kerman, Fars, Isfahan and Chahar Mahan and Bakhtaran with the total area of about thirty-five million hectares. As shown in this table, total volume of enhanced water has been estimated to about two thousand sixteen (2016) million cubic meters. Considering the total costs of cloud seeding operations, an average of eighteen point two Iranian Rails has been paid for each cubic meter of enhanced water. This is equal to about point five cent of US dollars, indicating that cloud seeding technology is an economic solution of water harvesting in arid regions.

Conclusion
The results of the present research showed that cloud seeding has been able to play an important role in water supply of Zayandehrud Dam, so that with the cloud seeding in the upstream of Zayandehrud Dam watersheds for several years, several million cubic meters of runoff has been produced and this is a way to reduce the adverse climate change impact. Investing in weather modification and doing it on a long-term and consecutive basis, as is done in many countries around the world, is one of the most cost-effective ways to produce water.